Breeding is energetically costly and, if energy-limited, birds may alter their time budgets, spen... more Breeding is energetically costly and, if energy-limited, birds may alter their time budgets, spending less time engaged in some activities and more time in others. Investigators who have provided breeding birds with supplemental food have noted changes in time budgets, but the extent and types of changes have been found to vary among species. Our objective was to determine how food supplementation might influence the time budgets and paternity status of male Indigo Buntings (Passerina cyanea). We studied Indigo Buntings from 8 May to 15 August 2009 in Madison County, Kentucky. Territories of male Indigo Buntings (n=30) were randomly assigned as either food supplemented (n=8) or controls (n=22). During time-budget observations, all behaviours were noted. To determine paternity status, blood samples were collected from adults and nestlings at 16 nests. Males with feeders in their territories spent significantly less time foraging and more time vocalising (chip notes) than males withou...
ABSTRACT Nestlings of some aerial insectivores experience pre-fledging mass recession, possibly t... more ABSTRACT Nestlings of some aerial insectivores experience pre-fledging mass recession, possibly to achieve optimum wing loading at fledging. However, studies to date where mass recession was linked to wing loading at fledging have been limited to 2 species of swifts (Apodidae), and additional studies are needed to determine if factors contributing to prefledging mass recession vary among species. We examined factors contributing to pre-fledging mass recession by nestling Tree Swallows (Tachycineta bicolor). During the 2015 breeding season in Kentucky, nestling Tree Swallows in 29 broods were divided into half-weighted, full-weighted, and control treatment groups. Lead weights weighing either 2.5% (0.6 g) or 5% (1.2 g) of nestling mass were glued to the back feathers of half-weighted and full-weighted nestlings, respectively, between 9 and 11 days post-hatching. Video recordings were used to monitor provisioning and begging behavior. Treatment groups did not differ in mass at fledging, amount of mass lost, or wing loading at fledging, and adult provisioning rates and time spent begging by nestlings did not vary from day 11 to day 19 post-hatching. Thus, mass loss by nestling Tree Swallows prior to fledging was not due to changes in either parental or nestling behavior, but likely resulted from loss of water from maturing feathers and other tissues. In contrast, studies of 2 species of swifts (Apodidae) revealed that changes in nestling behavior influenced pre-fledging mass recession, with weighted nestlings losing more mass than control nestlings, apparently to optimize wing loading at fledging. This difference between swifts and Tree Swallows may be due to differences in the duration of nestling periods (longer for swifts) and wing loading (higher in swifts). With greater wing loading, optimum mass at fledging may be more critical for swifts than Tree Swallows.
ABSTRACT Current evidence suggests that females in some species of songbirds engage in extra-terr... more ABSTRACT Current evidence suggests that females in some species of songbirds engage in extra-territorial forays, and that the function(s) of such forays varies among species. We examined the movements and behavior of 16 female Indigo Buntings (Passerina cyanea) in east-central Kentucky in an attempt to determine the possible function(s) of their extra-territorial forays. We used radiotelemetry to track the movements of 9 females paired with second-year (SY) males and 7 females paired with after-second-year (ASY) males. Radio-tagged female Indigo Buntings spent an average of 38% of their time off their mate's territories, with no difference in time spent off territory between females paired to SY and ASY males. In addition, the mean time that females spent off their social mate's territory did not vary with female fertility status (prefertile, fertile, or post-fertile). Our results suggest that, regardless of age, female Indigo Buntings did not seek to avoid, and may actively pursue, extrapair copulations when away from the territories of their social mates. Because the time spent in extra-territorial forays did not differ with female fertility status, such forays may also be important in providing females with useful information about their local environments and with access to additional foraging sites.
Carotenoid-based coloration of skin and plumage has been found to be correlated with individual q... more Carotenoid-based coloration of skin and plumage has been found to be correlated with individual quality in many species of birds during the breeding season. However, less is known about the possible role of these signals during the nonbreeding season, particularly among nonpasserines that defend winter territories. American Kestrels (Falco sparverius) are sexually dimorphic raptors that defend winter territories and possess carotenoid-based morphological features known to be correlated with individual quality. Much is known about winter territory use and habitat segregation by male and female kestrels, but possible relationships among morphological features, individual quality, and habitat quality have not been examined. Our objective was to examine possible relationships between morphology, territory quality, and skin color of American Kestrels. Male kestrels had brighter skin than females, and the skin color of male kestrels was positively correlated with size (wing chord and tail length) and territorial quality (hunting territories with less canopy and more grass cover). No such relationships were found for female kestrels. Skin color appears to be an honest indicator of quality for male American Kestrels and may serve both intersexual (territory acquisition) and intersexual (mate choice) functions during the breeding and nonbreeding seasons. Se ha encontrado que la coloración de plumas e integumento, asociada a la ingestión de carotenoides, está correlacionada con la calidad de individuos en muchas especies, durante la época reproductiva. Sin embargo, se conoce poco sobre el posible rol de estas señales durante la época no-reproductiva, particularmente entre paserinos que defienden territorios durante el invierno. Falco sparverius es un tipo de falcón sexualmente dimorfico que difiende territorio durante el invierno y tiene estructuras morfológicas cuyo pigmento está basado en carotenoides los cuales, a su vez, están correlacionados con la calidad de los individuos. Se conoce bastante sobre el uso de territorios durante el invierno y segregación de hábitat por parte de ambos sexos, pero nos se ha estudiado la posible relación entre aspectos morfológicos, la calidad de los individuos y la calidad del hábitat utilizado. Nuestro objetivo fue examinar la posible relación entre morfología, calidad del territorio y color del integumento en los falcones. El macho de la especie tiene un integumento más brillante que la hembra y el color de este se correlacionó positivamente con el tamano (largo del ala y el rabo) y la calidad del territorio (territorio de caceria con poco docel y más áreas abiertas con yerbas). No se encontró un correlación similar en las hembras. El color del integumento parece ser un buen
Sexual dimorphism or dichromatism has long been considered the result of sexual selection. Howeve... more Sexual dimorphism or dichromatism has long been considered the result of sexual selection. However, for many organisms the degree to which sexual dichromatism occurs has been determined within the confines of human perception. For birds, objective measures of plumage color have revealed previously unappreciated sexual dichromatism for several species. Here we present an unbiased assessment of plumage dichromatism in the yellow-breasted chat Icteria virens. Chats exhibit yellow to orange throat and breast plumage that to the unaided human observer differs only subtly in color. Spectrophotometric analyses revealed that chat throat and breast feathers exhibited reflective curves with two peaks, one in the ultraviolet and one in the yellow end of the spectrum. We found differences in both the shape and magnitude of reflectance curves between males and females. Moreover, for feathers collected from the lower edge and middle of the breast patch, male plumage reflected more light in the ultraviolet and yellow wavelengths compared to females, whereas male throat feathers appeared brighter than those of females only in the ultraviolet. Biochemical analyses indicated that the plumage pigmentation consisted solely of the carotenoid all-trans lutein and we found that males have higher concentrations of plumage carotenoids than females. Feathers that were naturally unpigmented reflected more UV light than yellow feathers, suggesting a potential role of feather microstructure in UV reflectance.
Individuals of many group-living species of birds respond to potential predators by giving alarm ... more Individuals of many group-living species of birds respond to potential predators by giving alarm calls, and some species give different, spatially referential alarm calls in response to aerial predators (raptors in flight) and terrestrial predators (including perched raptors). In black-capped chickadees, Poecile atricapillus, characteristics of alarm calls also vary with predator size and level of perceived threat , Science, 308, 1934-1937). We examined whether the terrestrial alarm calls of Carolina chickadees, P. carolinensis, show similar variation. In 2007 and 2008, we monitored responses of eight flocks of Carolina chickadees in Madison County, Kentucky, U.S.A. to mounts of different species of raptors that varied in size. Chickadees responded to the raptors by uttering 'chick-a-dee' calls with different numbers and types of notes. Larger, lower-threat predators (e.g. red-tailed hawk, Buteo jamaicensis) elicited calls with significantly more introductory 'chick' notes and fewer 'dee' notes, whereas smaller, higher-threat predators (e.g. eastern screech-owl, Megascops asio) elicited calls with few or no 'chick' notes and significantly more 'dee' notes. In addition, playback experiments revealed that a greater percentage of Carolina chickadees responded to playback of 'chick-a-dee' calls previously given in response to a small predator than during playback of calls given in response to a large predator. These results suggest that the 'chick-a-dee' alarm call is a graded signal that informs conspecifics about the presence and behaviour (i.e. perched) of a predator and the degree of threat posed by that predator.
We videotaped an Eastern Phoebe (Sayornis phoebe) nest in central Kentucky on 22 June 2008 and do... more We videotaped an Eastern Phoebe (Sayornis phoebe) nest in central Kentucky on 22 June 2008 and documented a case of infanticide. An adult male phoebe, likely the resident male, was captured at the nest site on 21 June 2008. The resident female fed nestlings (3, ,8 days of age) 69 times during a 4.1-hr taping session (0815-1221 hrs EDT) the next day, but the resident male was not observed at the nest. Beginning at 0923 hrs, an intruding phoebe (likely a male) occasionally visited the nest, sometimes pecking at, but not feeding, the nestlings; this phoebe initiated a vigorous attack at 1151 hrs, pecking and pulling the head of one of the nestlings for 25 min before pulling it out of the nest. The intruding phoebe returned after a short absence, just before the end of the videotape, and began attacking another nestling. The nest was empty when checked the next day. Suitable territories and nest sites may be limiting factors for Eastern Phoebes, and infanticide by non-breeding males may enhance their reproductive success if the resident female or a new female subsequently pairs with the male and initiates a new nest.
Descriptive studies of species with single-song repertoires may provide information potentially u... more Descriptive studies of species with single-song repertoires may provide information potentially useful in understanding the factors involved in the evolution of multisong repertoires. We studied the singing behavior of Henslow’s sparrows (Ammodramus henslowii) from April 21 to July 25, 2000 in west-central Kentucky. To examine song function and how males use single-song repertoires in intraspecifi c communication, we measured variation in singing rates within and among males, and compared the characteristics of songs sung in different behavioral contexts. Singing rates declined after pairing, suggesting that songs play a role in mate attraction. Male Henslow’s sparrows continued singing after pairing, although at lower rates, suggesting that singing serves functions other than mate attraction. Males were observed countersinging with neighboring males and sang after chasing trespassing males from their territories, suggesting that singing also functions in territory defense. Characte...
Reintroduction programs where captive-bred individuals are released into the wild have been used ... more Reintroduction programs where captive-bred individuals are released into the wild have been used in an attempt to increase declining populations of several species of birds. Scott and Carpenter (1987) suggested that reintroduction programs provide several potential benefits for small populations, such as increasing the number of animals, increasing genetic diversity, reducing inbreeding depression, and establishing new populations. However, reintroduction programs can also have negative impacts, including the introduction of diseases and parasites and potential genetic changes (Long 1981). Despite these potential impacts, reintroduction programs have been successful for several species of birds, includeing Peregrine Falcons (Falco peregrinus), Masked Bobwhite (Colinus virginianus ridgwayi), and Puerto Rican Parrots (Amazona vittata) (Scott and Carpenter 1987). In North America, evidence suggests that populations of Barn Owls (Tyto alba) have declined in recent years (Colvin et al. 1...
For sit-and-wait predators like Red-tailed Hawks (Buteojamaicensis), perch sites are important co... more For sit-and-wait predators like Red-tailed Hawks (Buteojamaicensis), perch sites are important components of hunting ranges. From October 1999-July 2000, perches (N = 270) used by Red-tailed Hawks in central Kentucky were located and characterized. Perches used by Red-tailed Hawks were relatively high (x = 12.3 m) in trees or on poles. Such perches provide a large, relatively unobstructed field of view and likely increase the chances of detecting prey. Red-tailed Hawks spent more time on perches before attacking than before giving up, perhaps waiting to attack prey after locating it to increase the chance of a successful attack. Characteristics of vegetation around perches used by hunting Redtailed Hawks differed from those of areas around available (but apparently unused) sites during both the breeding and nonbreeding seasons. During the breeding season, areas used by Red-tailed Hawks had less forb cover, lower vegetation density, and shorter vegetation than available areas. During the nonbreeding season, areas used by Red-tailed Hawks were characterized by less bare ground, more grass cover, less shrub cover, fewer small trees, decreased vegetation density, and shorter vegetation than available areas. In general, used areas provided less cover, which may increase prey vulnerability. K•¾ WORDS: Red-tailed Hawk; Buteo jamaicensis; giving-up tim• hunting;, perch site. SITIOS DE PERCHA Y COMPORTAMIENTO DE CAZA DE LOS GAVILANES DE COLA ROJA (BUTEO JAMAICENSIS) R•SUMEN.-Para los depredadores que se perchan a esperar sus presas como el gavilfin de cola roja (Buteo jamaicensis), los siftos de percha son componentes importantes de sus rangos de caza. Desde octubre de 1999 a Julio 2000, se localizaron y caracterizaron las perchas (N-270) usadas pot los gavilanes de cola roja en Kentucky central. Las perchas usadas pot los gavilanes de cola roja fueron
Descriptive studies of species with single-song repertoires may provide information potentially u... more Descriptive studies of species with single-song repertoires may provide information potentially useful in understanding the factors involved in the evolution of multisong repertoires. We studied the singing behavior of Henslow’s sparrows (Ammodramus henslowii) from April 21 to July 25, 2000 in west-central Kentucky. To examine song function and how males use single-song repertoires in intraspecifi c communication, we measured variation in singing rates within and among males, and compared the characteristics of songs sung in different behavioral contexts. Singing rates declined after pairing, suggesting that songs play a role in mate attraction. Male Henslow’s sparrows continued singing after pairing, although at lower rates, suggesting that singing serves functions other than mate attraction. Males were observed countersinging with neighboring males and sang after chasing trespassing males from their territories, suggesting that singing also functions in territory defense. Characte...
Most species of songbirds exhibit biparental care, but, for many taxa and species, little is know... more Most species of songbirds exhibit biparental care, but, for many taxa and species, little is known about the relative contributions of males and females in brooding and provisioning nestlings. Additional studies of the contributions of males and females in brooding and feeding nestlings are needed to better understand the respective roles of males and females as well as the factors that might contribute to interspecific variation in those roles. We examined the roles of adult male and female White-eyed Vireos (Vireo griseus) in brooding and provisioning nestlings in east-central Kentucky during the 1996 breeding season. Nests were located by monitoring adult behavior and checking likely nest sites. Once eggs hatched, nests were video-recorded to monitor the behavior of adults. Subsequent review of videos revealed that both male and female White-eyed Vireos brooded young and that males provisioned nestlings at higher rates than females. In contrast to males in many other species of songbirds, male White-eyed Vireos assisted in brooding young and provisioned nestlings at higher rates than their mates. One possible explanation for this is that low rates of extra-pair paternity might increase male confidence of their paternity status. Parental care provided by male White-eyed Vireos may also limit energy expenditure by their mates and increase the likelihood of females re-nesting if nests are predated or initiating second nesting attempts if initial attempts are successful.
When perched, several species of small falcons, including American Kestrels (Falco sparverius), o... more When perched, several species of small falcons, including American Kestrels (Falco sparverius), often pump their tails, but the possible function of this behaviour is unknown. Our objective was to use observations and experiments to examine the possible function(s) of tail-pumping by American Kestrels. Fieldwork was conducted from March 2015 to December 2015 at the Blue Grass Army Depot in Madison County, Kentucky. During observations of focal kestrels, we noted their behaviour (e.g. landing on a perch, hunting, or consuming prey), including when and how often they pumped their tails (i.e. rapid movement of the tail down, then back up to its original position). Kestrels typically tail-pumped when landing on a perch (mean = 4.1±0.2 pumps per 10 s) and consuming prey (mean = 2.4±0.2 pumps per 10 s). When hunting, kestrels tail-pumped at higher rates during the 30 s prior to attacking (mean = 1.1±0.3 pumps) than they did during the 30–60 s interval before an attack (mean = 0.3±0.1 pump...
Some species of birds use their vocalisations to communicate predator presence and the level of t... more Some species of birds use their vocalisations to communicate predator presence and the level of threat they pose, including two species of corvids (Corvidae), American Crows (Corvus brachyrhynchos) and Siberian Jays (Perisoreus infaustus). Our objective was to determine if Blue Jays (Cyanocitta cristata), another corvid, also use specific calls or vary the characteristics of certain calls to convey information about the level of threat posed by aerial predators. During the non-breeding seasons of 2014 and 2015, we recorded and analysed the vocal responses of Blue Jays to study skins of six species of raptors that varied in size and the level of threat they pose to Blue Jays. Experiments were conducted at seven locations in Madison County, Kentucky. The mean number of Blue Jays present during trials was 2.6, and Blue Jays uttered five different vocalisations during trials, with ditonal and monotonal jeers given most frequently. The rate at which Blue Jays uttered ditonal jeers differ...
Little is known about how variation in nestling begging intensity influences the behaviour of adu... more Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestl...
Abstract Although most owls exhibit biparental care, the relative contributions of males and fema... more Abstract Although most owls exhibit biparental care, the relative contributions of males and females during critical life cycle stages are poorly understood. Further information could improve our understanding of the feeding ecology of owls and of mechanisms that govern natural and sexual selection, particularly as they relate to the evolution of reversed sexual dimorphism. The objective of our study was to assess possible intersexual differences in provisioning behavior (visit rate and prey size and type) of slightly dimorphic Eastern Screech-Owls (Megascops asio; females 17% greater mass than males) during the post-brooding period when both adults provision nestlings. Pairs of Eastern Screech-Owls provisioned young with 16 different types of prey in our study with insects and crayfish (Family Astacidae) being the most common. We found no differences between females and males in provisioning rate or in mean size of prey delivered. Our findings suggest Screech-Owls are opportunistic feeders in the post-brooding period and that food niche partitioning does not occur between the sexes. These findings are inconsistent with the Role Differentiation and Ecological Hypotheses made for the evolution of reversed sexual dimorphism but support the Rate Ingestion Hypothesis which predicts that both sexes may take smaller prey during the post-brooding period to increase ingestion rate and decrease handling time. In addition our results contribute to an understanding of the feeding ecology and life history of one of the most widespread and recognizable raptors in North America.
Breeding is energetically costly and, if energy-limited, birds may alter their time budgets, spen... more Breeding is energetically costly and, if energy-limited, birds may alter their time budgets, spending less time engaged in some activities and more time in others. Investigators who have provided breeding birds with supplemental food have noted changes in time budgets, but the extent and types of changes have been found to vary among species. Our objective was to determine how food supplementation might influence the time budgets and paternity status of male Indigo Buntings (Passerina cyanea). We studied Indigo Buntings from 8 May to 15 August 2009 in Madison County, Kentucky. Territories of male Indigo Buntings (n=30) were randomly assigned as either food supplemented (n=8) or controls (n=22). During time-budget observations, all behaviours were noted. To determine paternity status, blood samples were collected from adults and nestlings at 16 nests. Males with feeders in their territories spent significantly less time foraging and more time vocalising (chip notes) than males withou...
ABSTRACT Nestlings of some aerial insectivores experience pre-fledging mass recession, possibly t... more ABSTRACT Nestlings of some aerial insectivores experience pre-fledging mass recession, possibly to achieve optimum wing loading at fledging. However, studies to date where mass recession was linked to wing loading at fledging have been limited to 2 species of swifts (Apodidae), and additional studies are needed to determine if factors contributing to prefledging mass recession vary among species. We examined factors contributing to pre-fledging mass recession by nestling Tree Swallows (Tachycineta bicolor). During the 2015 breeding season in Kentucky, nestling Tree Swallows in 29 broods were divided into half-weighted, full-weighted, and control treatment groups. Lead weights weighing either 2.5% (0.6 g) or 5% (1.2 g) of nestling mass were glued to the back feathers of half-weighted and full-weighted nestlings, respectively, between 9 and 11 days post-hatching. Video recordings were used to monitor provisioning and begging behavior. Treatment groups did not differ in mass at fledging, amount of mass lost, or wing loading at fledging, and adult provisioning rates and time spent begging by nestlings did not vary from day 11 to day 19 post-hatching. Thus, mass loss by nestling Tree Swallows prior to fledging was not due to changes in either parental or nestling behavior, but likely resulted from loss of water from maturing feathers and other tissues. In contrast, studies of 2 species of swifts (Apodidae) revealed that changes in nestling behavior influenced pre-fledging mass recession, with weighted nestlings losing more mass than control nestlings, apparently to optimize wing loading at fledging. This difference between swifts and Tree Swallows may be due to differences in the duration of nestling periods (longer for swifts) and wing loading (higher in swifts). With greater wing loading, optimum mass at fledging may be more critical for swifts than Tree Swallows.
ABSTRACT Current evidence suggests that females in some species of songbirds engage in extra-terr... more ABSTRACT Current evidence suggests that females in some species of songbirds engage in extra-territorial forays, and that the function(s) of such forays varies among species. We examined the movements and behavior of 16 female Indigo Buntings (Passerina cyanea) in east-central Kentucky in an attempt to determine the possible function(s) of their extra-territorial forays. We used radiotelemetry to track the movements of 9 females paired with second-year (SY) males and 7 females paired with after-second-year (ASY) males. Radio-tagged female Indigo Buntings spent an average of 38% of their time off their mate's territories, with no difference in time spent off territory between females paired to SY and ASY males. In addition, the mean time that females spent off their social mate's territory did not vary with female fertility status (prefertile, fertile, or post-fertile). Our results suggest that, regardless of age, female Indigo Buntings did not seek to avoid, and may actively pursue, extrapair copulations when away from the territories of their social mates. Because the time spent in extra-territorial forays did not differ with female fertility status, such forays may also be important in providing females with useful information about their local environments and with access to additional foraging sites.
Carotenoid-based coloration of skin and plumage has been found to be correlated with individual q... more Carotenoid-based coloration of skin and plumage has been found to be correlated with individual quality in many species of birds during the breeding season. However, less is known about the possible role of these signals during the nonbreeding season, particularly among nonpasserines that defend winter territories. American Kestrels (Falco sparverius) are sexually dimorphic raptors that defend winter territories and possess carotenoid-based morphological features known to be correlated with individual quality. Much is known about winter territory use and habitat segregation by male and female kestrels, but possible relationships among morphological features, individual quality, and habitat quality have not been examined. Our objective was to examine possible relationships between morphology, territory quality, and skin color of American Kestrels. Male kestrels had brighter skin than females, and the skin color of male kestrels was positively correlated with size (wing chord and tail length) and territorial quality (hunting territories with less canopy and more grass cover). No such relationships were found for female kestrels. Skin color appears to be an honest indicator of quality for male American Kestrels and may serve both intersexual (territory acquisition) and intersexual (mate choice) functions during the breeding and nonbreeding seasons. Se ha encontrado que la coloración de plumas e integumento, asociada a la ingestión de carotenoides, está correlacionada con la calidad de individuos en muchas especies, durante la época reproductiva. Sin embargo, se conoce poco sobre el posible rol de estas señales durante la época no-reproductiva, particularmente entre paserinos que defienden territorios durante el invierno. Falco sparverius es un tipo de falcón sexualmente dimorfico que difiende territorio durante el invierno y tiene estructuras morfológicas cuyo pigmento está basado en carotenoides los cuales, a su vez, están correlacionados con la calidad de los individuos. Se conoce bastante sobre el uso de territorios durante el invierno y segregación de hábitat por parte de ambos sexos, pero nos se ha estudiado la posible relación entre aspectos morfológicos, la calidad de los individuos y la calidad del hábitat utilizado. Nuestro objetivo fue examinar la posible relación entre morfología, calidad del territorio y color del integumento en los falcones. El macho de la especie tiene un integumento más brillante que la hembra y el color de este se correlacionó positivamente con el tamano (largo del ala y el rabo) y la calidad del territorio (territorio de caceria con poco docel y más áreas abiertas con yerbas). No se encontró un correlación similar en las hembras. El color del integumento parece ser un buen
Sexual dimorphism or dichromatism has long been considered the result of sexual selection. Howeve... more Sexual dimorphism or dichromatism has long been considered the result of sexual selection. However, for many organisms the degree to which sexual dichromatism occurs has been determined within the confines of human perception. For birds, objective measures of plumage color have revealed previously unappreciated sexual dichromatism for several species. Here we present an unbiased assessment of plumage dichromatism in the yellow-breasted chat Icteria virens. Chats exhibit yellow to orange throat and breast plumage that to the unaided human observer differs only subtly in color. Spectrophotometric analyses revealed that chat throat and breast feathers exhibited reflective curves with two peaks, one in the ultraviolet and one in the yellow end of the spectrum. We found differences in both the shape and magnitude of reflectance curves between males and females. Moreover, for feathers collected from the lower edge and middle of the breast patch, male plumage reflected more light in the ultraviolet and yellow wavelengths compared to females, whereas male throat feathers appeared brighter than those of females only in the ultraviolet. Biochemical analyses indicated that the plumage pigmentation consisted solely of the carotenoid all-trans lutein and we found that males have higher concentrations of plumage carotenoids than females. Feathers that were naturally unpigmented reflected more UV light than yellow feathers, suggesting a potential role of feather microstructure in UV reflectance.
Individuals of many group-living species of birds respond to potential predators by giving alarm ... more Individuals of many group-living species of birds respond to potential predators by giving alarm calls, and some species give different, spatially referential alarm calls in response to aerial predators (raptors in flight) and terrestrial predators (including perched raptors). In black-capped chickadees, Poecile atricapillus, characteristics of alarm calls also vary with predator size and level of perceived threat , Science, 308, 1934-1937). We examined whether the terrestrial alarm calls of Carolina chickadees, P. carolinensis, show similar variation. In 2007 and 2008, we monitored responses of eight flocks of Carolina chickadees in Madison County, Kentucky, U.S.A. to mounts of different species of raptors that varied in size. Chickadees responded to the raptors by uttering 'chick-a-dee' calls with different numbers and types of notes. Larger, lower-threat predators (e.g. red-tailed hawk, Buteo jamaicensis) elicited calls with significantly more introductory 'chick' notes and fewer 'dee' notes, whereas smaller, higher-threat predators (e.g. eastern screech-owl, Megascops asio) elicited calls with few or no 'chick' notes and significantly more 'dee' notes. In addition, playback experiments revealed that a greater percentage of Carolina chickadees responded to playback of 'chick-a-dee' calls previously given in response to a small predator than during playback of calls given in response to a large predator. These results suggest that the 'chick-a-dee' alarm call is a graded signal that informs conspecifics about the presence and behaviour (i.e. perched) of a predator and the degree of threat posed by that predator.
We videotaped an Eastern Phoebe (Sayornis phoebe) nest in central Kentucky on 22 June 2008 and do... more We videotaped an Eastern Phoebe (Sayornis phoebe) nest in central Kentucky on 22 June 2008 and documented a case of infanticide. An adult male phoebe, likely the resident male, was captured at the nest site on 21 June 2008. The resident female fed nestlings (3, ,8 days of age) 69 times during a 4.1-hr taping session (0815-1221 hrs EDT) the next day, but the resident male was not observed at the nest. Beginning at 0923 hrs, an intruding phoebe (likely a male) occasionally visited the nest, sometimes pecking at, but not feeding, the nestlings; this phoebe initiated a vigorous attack at 1151 hrs, pecking and pulling the head of one of the nestlings for 25 min before pulling it out of the nest. The intruding phoebe returned after a short absence, just before the end of the videotape, and began attacking another nestling. The nest was empty when checked the next day. Suitable territories and nest sites may be limiting factors for Eastern Phoebes, and infanticide by non-breeding males may enhance their reproductive success if the resident female or a new female subsequently pairs with the male and initiates a new nest.
Descriptive studies of species with single-song repertoires may provide information potentially u... more Descriptive studies of species with single-song repertoires may provide information potentially useful in understanding the factors involved in the evolution of multisong repertoires. We studied the singing behavior of Henslow’s sparrows (Ammodramus henslowii) from April 21 to July 25, 2000 in west-central Kentucky. To examine song function and how males use single-song repertoires in intraspecifi c communication, we measured variation in singing rates within and among males, and compared the characteristics of songs sung in different behavioral contexts. Singing rates declined after pairing, suggesting that songs play a role in mate attraction. Male Henslow’s sparrows continued singing after pairing, although at lower rates, suggesting that singing serves functions other than mate attraction. Males were observed countersinging with neighboring males and sang after chasing trespassing males from their territories, suggesting that singing also functions in territory defense. Characte...
Reintroduction programs where captive-bred individuals are released into the wild have been used ... more Reintroduction programs where captive-bred individuals are released into the wild have been used in an attempt to increase declining populations of several species of birds. Scott and Carpenter (1987) suggested that reintroduction programs provide several potential benefits for small populations, such as increasing the number of animals, increasing genetic diversity, reducing inbreeding depression, and establishing new populations. However, reintroduction programs can also have negative impacts, including the introduction of diseases and parasites and potential genetic changes (Long 1981). Despite these potential impacts, reintroduction programs have been successful for several species of birds, includeing Peregrine Falcons (Falco peregrinus), Masked Bobwhite (Colinus virginianus ridgwayi), and Puerto Rican Parrots (Amazona vittata) (Scott and Carpenter 1987). In North America, evidence suggests that populations of Barn Owls (Tyto alba) have declined in recent years (Colvin et al. 1...
For sit-and-wait predators like Red-tailed Hawks (Buteojamaicensis), perch sites are important co... more For sit-and-wait predators like Red-tailed Hawks (Buteojamaicensis), perch sites are important components of hunting ranges. From October 1999-July 2000, perches (N = 270) used by Red-tailed Hawks in central Kentucky were located and characterized. Perches used by Red-tailed Hawks were relatively high (x = 12.3 m) in trees or on poles. Such perches provide a large, relatively unobstructed field of view and likely increase the chances of detecting prey. Red-tailed Hawks spent more time on perches before attacking than before giving up, perhaps waiting to attack prey after locating it to increase the chance of a successful attack. Characteristics of vegetation around perches used by hunting Redtailed Hawks differed from those of areas around available (but apparently unused) sites during both the breeding and nonbreeding seasons. During the breeding season, areas used by Red-tailed Hawks had less forb cover, lower vegetation density, and shorter vegetation than available areas. During the nonbreeding season, areas used by Red-tailed Hawks were characterized by less bare ground, more grass cover, less shrub cover, fewer small trees, decreased vegetation density, and shorter vegetation than available areas. In general, used areas provided less cover, which may increase prey vulnerability. K•¾ WORDS: Red-tailed Hawk; Buteo jamaicensis; giving-up tim• hunting;, perch site. SITIOS DE PERCHA Y COMPORTAMIENTO DE CAZA DE LOS GAVILANES DE COLA ROJA (BUTEO JAMAICENSIS) R•SUMEN.-Para los depredadores que se perchan a esperar sus presas como el gavilfin de cola roja (Buteo jamaicensis), los siftos de percha son componentes importantes de sus rangos de caza. Desde octubre de 1999 a Julio 2000, se localizaron y caracterizaron las perchas (N-270) usadas pot los gavilanes de cola roja en Kentucky central. Las perchas usadas pot los gavilanes de cola roja fueron
Descriptive studies of species with single-song repertoires may provide information potentially u... more Descriptive studies of species with single-song repertoires may provide information potentially useful in understanding the factors involved in the evolution of multisong repertoires. We studied the singing behavior of Henslow’s sparrows (Ammodramus henslowii) from April 21 to July 25, 2000 in west-central Kentucky. To examine song function and how males use single-song repertoires in intraspecifi c communication, we measured variation in singing rates within and among males, and compared the characteristics of songs sung in different behavioral contexts. Singing rates declined after pairing, suggesting that songs play a role in mate attraction. Male Henslow’s sparrows continued singing after pairing, although at lower rates, suggesting that singing serves functions other than mate attraction. Males were observed countersinging with neighboring males and sang after chasing trespassing males from their territories, suggesting that singing also functions in territory defense. Characte...
Most species of songbirds exhibit biparental care, but, for many taxa and species, little is know... more Most species of songbirds exhibit biparental care, but, for many taxa and species, little is known about the relative contributions of males and females in brooding and provisioning nestlings. Additional studies of the contributions of males and females in brooding and feeding nestlings are needed to better understand the respective roles of males and females as well as the factors that might contribute to interspecific variation in those roles. We examined the roles of adult male and female White-eyed Vireos (Vireo griseus) in brooding and provisioning nestlings in east-central Kentucky during the 1996 breeding season. Nests were located by monitoring adult behavior and checking likely nest sites. Once eggs hatched, nests were video-recorded to monitor the behavior of adults. Subsequent review of videos revealed that both male and female White-eyed Vireos brooded young and that males provisioned nestlings at higher rates than females. In contrast to males in many other species of songbirds, male White-eyed Vireos assisted in brooding young and provisioned nestlings at higher rates than their mates. One possible explanation for this is that low rates of extra-pair paternity might increase male confidence of their paternity status. Parental care provided by male White-eyed Vireos may also limit energy expenditure by their mates and increase the likelihood of females re-nesting if nests are predated or initiating second nesting attempts if initial attempts are successful.
When perched, several species of small falcons, including American Kestrels (Falco sparverius), o... more When perched, several species of small falcons, including American Kestrels (Falco sparverius), often pump their tails, but the possible function of this behaviour is unknown. Our objective was to use observations and experiments to examine the possible function(s) of tail-pumping by American Kestrels. Fieldwork was conducted from March 2015 to December 2015 at the Blue Grass Army Depot in Madison County, Kentucky. During observations of focal kestrels, we noted their behaviour (e.g. landing on a perch, hunting, or consuming prey), including when and how often they pumped their tails (i.e. rapid movement of the tail down, then back up to its original position). Kestrels typically tail-pumped when landing on a perch (mean = 4.1±0.2 pumps per 10 s) and consuming prey (mean = 2.4±0.2 pumps per 10 s). When hunting, kestrels tail-pumped at higher rates during the 30 s prior to attacking (mean = 1.1±0.3 pumps) than they did during the 30–60 s interval before an attack (mean = 0.3±0.1 pump...
Some species of birds use their vocalisations to communicate predator presence and the level of t... more Some species of birds use their vocalisations to communicate predator presence and the level of threat they pose, including two species of corvids (Corvidae), American Crows (Corvus brachyrhynchos) and Siberian Jays (Perisoreus infaustus). Our objective was to determine if Blue Jays (Cyanocitta cristata), another corvid, also use specific calls or vary the characteristics of certain calls to convey information about the level of threat posed by aerial predators. During the non-breeding seasons of 2014 and 2015, we recorded and analysed the vocal responses of Blue Jays to study skins of six species of raptors that varied in size and the level of threat they pose to Blue Jays. Experiments were conducted at seven locations in Madison County, Kentucky. The mean number of Blue Jays present during trials was 2.6, and Blue Jays uttered five different vocalisations during trials, with ditonal and monotonal jeers given most frequently. The rate at which Blue Jays uttered ditonal jeers differ...
Little is known about how variation in nestling begging intensity influences the behaviour of adu... more Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestl...
Abstract Although most owls exhibit biparental care, the relative contributions of males and fema... more Abstract Although most owls exhibit biparental care, the relative contributions of males and females during critical life cycle stages are poorly understood. Further information could improve our understanding of the feeding ecology of owls and of mechanisms that govern natural and sexual selection, particularly as they relate to the evolution of reversed sexual dimorphism. The objective of our study was to assess possible intersexual differences in provisioning behavior (visit rate and prey size and type) of slightly dimorphic Eastern Screech-Owls (Megascops asio; females 17% greater mass than males) during the post-brooding period when both adults provision nestlings. Pairs of Eastern Screech-Owls provisioned young with 16 different types of prey in our study with insects and crayfish (Family Astacidae) being the most common. We found no differences between females and males in provisioning rate or in mean size of prey delivered. Our findings suggest Screech-Owls are opportunistic feeders in the post-brooding period and that food niche partitioning does not occur between the sexes. These findings are inconsistent with the Role Differentiation and Ecological Hypotheses made for the evolution of reversed sexual dimorphism but support the Rate Ingestion Hypothesis which predicts that both sexes may take smaller prey during the post-brooding period to increase ingestion rate and decrease handling time. In addition our results contribute to an understanding of the feeding ecology and life history of one of the most widespread and recognizable raptors in North America.
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