Papers by Cecilia Kullberg
Ambio, 2015
Many migratory bird species have advanced their spring arrival during the latest decades, most pr... more Many migratory bird species have advanced their spring arrival during the latest decades, most probably due to climate change. However, studies on migratory phenology in the period before recent global warming are scarce. We have analyzed a historical dataset (1873-1917) of spring arrival to southern and central Sweden of 14 migratory bird species. In addition, we have used relative differences between historical and present-day observations (1984-2013) to evaluate the effect of latitude and migratory strategy on day of arrival over time. There was a larger change in spring phenology in short-distance migrants than in long-distance migrants. Interestingly, the results further suggest that climate change has affected the phenology of short-distance migrants more in southern than in central Sweden. The results suggest that the much earlier calculated arrival to southern Sweden among short-distance migrants mirrors a change in location of wintering areas, hence, connecting migration ph...
Current Ornithology Volume 17, 2010
Because the failure to escape a predator causes death to a prey animal, and thus excludes opportu... more Because the failure to escape a predator causes death to a prey animal, and thus excludes opportunities to reproduce in the future, predation is a major selective force in nature (e.g., Lima and Dill 1990; Dawkins and Krebs 1979). To evade attacks from an array of different predators successfully is thus of key importance for all potential prey organisms. In most animals there are periods in their life when they are more susceptible to predation than at other times. For example, the reproductive period might be associated with enhanced predation risk (see Magnhagen 1991 for a review). In birds, the most common way of escaping from predators is to use the ability to fly, and when birds are attacked by predators, take-off ability and maneuverability in flight are crucial for survival (e.g., Rudebeck 1950). Changes in body mass or wing area will change wing load (body mass/wing area, see Pennycuick 1989) and thus potentially will affect flight ability. Such changes in wing load may lead to variation in predation risk during a bird’s life. Periods when birds may have impaired evasive abilities because of changes in wing load include during migration (increased mass from fat storage), reproduction (increased mass from egg load), and molt (reduced wing area from feather loss and growth).
Location is everything and the geographical distribution of populations will make them differenti... more Location is everything and the geographical distribution of populations will make them differentially affected by global warming. Sweden’s north to south orientation presents a great frame for studying the effect of latitudinal climate change. We present a long-term study on the migratory behaviour of two populations of Willow Warbler subspecies (southern Phylloscopus trochilus trochilus and northern P.t. acredula). The material covers a 31-year period and is analysed in relation to climatic indices. Three study sites are considered, the island of Gotland in southern Sweden (ringing recoveries 1990-2012, breeding data 1992-93, 2011-13) and in northern Sweden Abisko (breeding data 2011-13) and Haparanda (autumn ringing recoveries 1982-2012).We found that the both the spring passage over Gotland and the arrival of breeding birds to the island have advanced significantly by 0.38 days/year. Egg-laying dates have also advanced and are now 5days earlier than in the 1990s. The degree of pr...
Animal Cognition
Individuals often produce alarm or mobbing calls when they detect a threat such as a predator. Li... more Individuals often produce alarm or mobbing calls when they detect a threat such as a predator. Little is known about whether such calling is affected by the facial orientation of a potential threat, however. We tested for an effect of facial orientation of a potential threat on tufted titmice, Baeolophus bicolor, a songbird that uses chick-a-dee calls in a variety of social contexts. In two studies, a human observer wore an animal mask that either faced or faced away from the focal bird(s). In Study 1, focal birds were individual titmice captured in a walk-in trap, and the observer stood near the trapped bird. In Study 2, focal birds were titmouse flocks utilizing a feeding station and the observer stood near the station. In both studies, calling behavior was affected by mask orientation. In Study 2, foraging and agonistic behavior were also affected. Titmice can therefore perceive the facial orientation of a potential threat, and this perception affects different behavioral systems...
Journal of Avian Biology, 2014
ABSTRACT Migratory birds use stopovers to replenish their fuel reserves and they generally spend ... more ABSTRACT Migratory birds use stopovers to replenish their fuel reserves and they generally spend more time at stopover sites than they do in actual flight. When arriving at a new stopover site birds may need to search extensively to find a suitable feeding area and this search and settling period may affect the duration of stopover. Stopover behaviour can thus have profound effects on the migratory programme and studies on stopover behaviour are important to understand migratory strategies. We followed 51 first-year garden warblers Sylvia borin with radio-transmitters at an autumn stopover site on the island of Gotland in southern Sweden. Our aim was to determine the distance birds relocated from the coastal capture site when searching for an area to settle in, and also to establish the duration of stopover and put it in relation to refuelling rate by recapturing a subset of the radio-tracked individuals. Sixteen birds made an extended stopover (> 2 d), relocated inland from the capture site and settled on average 5.6 km from the capture site, with the longest recorded relocation being fourteen kilometres. Birds that relocated nocturnally settled in areas further away than birds that relocated diurnally. Thirteen birds that continued migration after a short stop carried larger fuel stores than birds that stopped over longer and they remained close to the capture site until departure. Three birds were re-trapped and showed high fuelling rates, between 0.3 and 1.1 g d–1. They left the stopover site with fuel loads between 40–56 percent of lean body mass, which possibly would have allowed them to reach the Mediterranean area without additional refuelling stops.
Scientific Reports, 2012
Reciprocity is fundamental to cooperative behaviour and has been verified in theoretical models. ... more Reciprocity is fundamental to cooperative behaviour and has been verified in theoretical models. However, there is still limited experimental evidence for reciprocity in non-primate species. Our results more decisively clarify that reciprocity with a tit-for-tat enforcement strategy can occur among breeding pied flycatchers Ficedula hypoleuca separate from considerations of byproduct mutualism. Breeding pairs living in close proximity (20-24 m) did exhibit byproduct mutualism and always assisted in mobbing regardless of their neighbours' prior actions. However, breeding pairs with distant neighbours (69-84 m) either assisted or refused to assist in mobbing a predatory owl based on whether or not the distant pair had previously helped them in their own nest defense against the predator. Clearly, these birds are aware of their specific spatial security context, remember their neighbours' prior behaviour, and choose a situation-specific strategic course of action, which could promote their longer-term security, a capacity previously thought unique to primates.
PeerJ, 2014
Garden Warblers Sylvia borin were studied during autumn stopover in Crete before crossing the bar... more Garden Warblers Sylvia borin were studied during autumn stopover in Crete before crossing the barrier of the Mediterranean Sea and the Sahara Desert. Birds followed with transmitters show extensive stopover periods, which were longer in first-year birds, 16 days, compared with adult birds, 14 days. The distribution of body masses from birds trapped in fig trees were used to estimate the departure body mass and the results found indicate that both age categories on average depart with a fuel load close to 100% of lean body mass. The movement of transmitter birds shows differences between first-year and adult birds. Adult birds move further away from the release site and many also left the study area. Several were found settled outside the study area, up to 17 km away, indicating that they regularly make longer stopover movements. It is suggested that this might be a result of that they return to a place where they stayed during an earlier migration. It was shown that stopover site fidelity exists and nine garden warblers were recaptured in the area during a following autumn. The results found highlights the importance of stopover areas close to the Sahara Desert.
Journal of Avian Biology, 2014
ABSTRACT Climate change can influence many aspects of avian phenology and especially migratory sh... more ABSTRACT Climate change can influence many aspects of avian phenology and especially migratory shifts and changes in breeding onset receive much research interest in this context. However, changes in these different life-cycle events in birds are often investigated separately and by means of ringing records of mixed populations. In this long-term study on the willow warbler Phylloscopus trochilus, we investigated timing of spring and autumn migration in conjunction with timing of breeding. We made distinction among individuals with regard to age, sex, juvenile origin and migratory phase. The data set comprised 22-yr of ringing records and two temporally separated data sets of egg-laying dates and arrival of the breeding population close to the ringing site. The results reveal an overall advancement consistent in most, but not all, phenological events. During spring migration, early and median passage of males and females became earlier by between 4.4 to 6.3 d and median egg-laying dates became earlier by 5 d. Male arrival advanced more, which may lead to an increase in the degree of protandry in the future. Among breeding individuals, only female arrival advanced in timing. In autumn, adults and locally hatched juvenile females did not advanced median passage, but locally hatched juvenile males appeared 4.2 d earlier. Migrating juvenile males and females advanced passage both in early and median migratory phase by between 8.4 to 10.1 d. The dissimilarities in the response between birds of different age, sex and migratory phase emphasize that environmental change may elicit intra-specific selection pressures. The overall consistency of the phenological change in spring, autumn and egg-laying, coupled with the unchanged number of days between median spring and autumn migration in adults, indicate that the breeding area residence has advanced seasonally but remained temporally constant.
Ambio, 2015
Many migratory bird species have advanced their spring arrival during the latest decades, most pr... more Many migratory bird species have advanced their spring arrival during the latest decades, most probably due to climate change. However, studies on migratory phenology in the period before recent global warming are scarce. We have analyzed a historical dataset (1873-1917) of spring arrival to southern and central Sweden of 14 migratory bird species. In addition, we have used relative differences between historical and present-day observations (1984-2013) to evaluate the effect of latitude and migratory strategy on day of arrival over time. There was a larger change in spring phenology in short-distance migrants than in long-distance migrants. Interestingly, the results further suggest that climate change has affected the phenology of short-distance migrants more in southern than in central Sweden. The results suggest that the much earlier calculated arrival to southern Sweden among short-distance migrants mirrors a change in location of wintering areas, hence, connecting migration ph...
Journal of Experimental Biology, 2008
Recent studies have shown that migratory thrush nightingales (Luscinia luscinia) experimentally t... more Recent studies have shown that migratory thrush nightingales (Luscinia luscinia) experimentally treated with multiple changes of the magnetic field simulating a journey to their target stopover area in northern Egypt, increased fuel deposition as expected in preparation to cross the Sahara desert. To investigate the significance of food intake on the body mass changes observed, in the work described here we analysed food intake of the nightingales under study in those earlier experiments. Furthermore, to study whether a single change in the magnetic field directly to northern Egypt is sufficient to provide information for fuelling decisions, we performed a new experiment, exposing thrush nightingales trapped in Sweden, directly to a magnetic field of northern Egypt. Our results show that an experimentally induced magnetic field of northern Egypt, close to the barrier crossing, triggers the same response in fuel deposition as experiments with multiple changes of the magnetic field simulating a migratory journey from Sweden to Egypt, suggesting that migratory birds do not require successive changes in field parameters to incorporate magnetic information into their migratory program. Furthermore, irrespective of experimental set up (single or multiple changes of the magnetic field parameters) increase in food intake seems to be the major reason for the observed increase in fuelling rate compared with control birds, suggesting that geomagnetic information might trigger hormonal changes in migratory birds enabling appropriate fuelling behaviour during migration.
Journal of Experimental Biology, 2008
For an animal to escape an attacking predator, speed and manoeuvrability are likely to be crucial... more For an animal to escape an attacking predator, speed and manoeuvrability are likely to be crucial factors. Previous studies on reptiles and birds have revealed that gaining weight, due to for instance egg load or lipid accumulation, leads to impaired escape ability and possibly increases the risk of being caught by predators. Here we tested whether the flight performance of an insect, the small tortoiseshell butterfly (Aglais urticae), is affected by variations in body mass due to feeding by comparing flight performance parameters between individuals that (i) took flight spontaneously or after being subjected to a simulated predator attack and (ii) varied in flight muscle ratio (FMR: thorax mass/total body mass). The results show that butterflies that were subjected to a simulated predator attack flew at higher velocities and straighter than butterflies that were allowed to take off spontaneously. Furthermore, our study suggests, for the first time, that butterflies may experience impaired escape ability after feeding, which directly leads to a decrease in FMR; a reduction from 0.5 to 0.3 reduced escape flight velocity by about 37% at 0.5 m from the start. Finally, this study shows that FMR affects take-off angle and sinuosity, with steeper angles and more turning in butterflies with low FMR.
Proceedings of the Royal Society B: Biological Sciences, 1996
Proceedings of the Royal Society B: Biological Sciences, 2003
Bird migration requires high energy expenditure, and long-distance migrants accumulate fat for us... more Bird migration requires high energy expenditure, and long-distance migrants accumulate fat for use as fuel during stopovers throughout their journey. Recent studies have shown that long-distance migratory birds, besides accumulating fat for use as fuel, also show adaptive phenotypic flexibility in several organs during migration. The migratory routes of many songbirds include stretches of sea and desert where fuelling is not possible. Large fuel loads increase flight costs and predation risk, therefore extensive fuelling should occur only immediately prior to crossing inhospitable zones. However, despite their crucial importance for the survival of migratory birds, both strategic refuelling decisions and variation in phenotypic flexibility during migration are not well understood. First-year thrush nightingales (Luscinia luscinia) caught in the early phase of the onset of autumn migration in southeast Sweden and exposed to a magnetic treatment simulating a migratory flight to northern Egypt increased more in fuel load than control birds. By contrast, birds trapped during the late phase of the onset of autumn migration accumulated a high fuel load irrespective of magnetic treatment. Furthermore, early birds increased less in flight-muscle size than birds trapped later in autumn. We suggest that the relative importance of endogenous and environmental factors in individual birds is affected by the time of season and by geographical area. When approaching a barrier, environmental cues may act irrespective of the endogenous time programme.
Proceedings of the Royal Society B: Biological Sciences, 1998
When birds are attacked by predators the initial take-o¡ is crucial for survival. The strategy in... more When birds are attacked by predators the initial take-o¡ is crucial for survival. The strategy in the initial phase of predator evasion is probably a¡ected by factors such as body mass and presence of cover and conspeci¢cs, but it may also be a response to the character of the predator's attack. In choosing an angle of £ight, birds face a trade-o¡ between climbing from the ground and accelerating across the ground. This is, to our knowledge, the ¢rst study investigating whether the attack trajectory of a raptor a¡ects the take-o¡ strategy of the prey bird. First-year male great tits (Parus major) adjusted take-o¡ angle to a model predator's angle of attack. Birds attacked from a steep angle took o¡ at a lower angle than birds attacked from a low angle. We also compared take-o¡s at dawn and dusk but could not ¢nd any measurable e¡ect of the diurnal body mass gain (on average 7.9%) in the great tits on either £ight velocity or angle of ascent.
Proceedings of the Royal Society B: Biological Sciences, 2007
Recent evaluations of both temporal and spatial precision in bird migration have called for exter... more Recent evaluations of both temporal and spatial precision in bird migration have called for external cues in addition to the inherited programme defining the migratory journey in terms of direction, distance and fuelling behaviour along the route. We used juvenile European robins (Erithacus rubecula) to study whether geomagnetic cues affect fuel deposition in a medium-distance migrant by simulating a migratory journey from southeast Sweden to the wintering area in southern Spain. In the late phase of the onset of autumn migration, robins exposed to the magnetic treatment attained a lower fuel load than control birds exposed to the ambient magnetic field of southeast Sweden. In contrast, robins captured in the early phase of the onset of autumn migration all showed low fuel deposition irrespective of experimental treatment. These results are, as expected, the inverse of what we have found in similar studies in a long-distance migrant, the thrush nightingale (Luscinia luscinia), indicating that the reaction in terms of fuelling behaviour to a simulated southward migration varies depending on the relevance for the species. Furthermore, we suggest that information from the geomagnetic field act as an important external cue overriding the seasonal effect on fuelling behaviour in migratory birds.
Philosophical Transactions of The Royal Society B Biological Sciences
The Paridae family (chickadees, tits and titmice) is an interesting avian group in that species v... more The Paridae family (chickadees, tits and titmice) is an interesting avian group in that species vary in important aspects of their social structure and many species have large and complex vocal repertoires. For this reason, parids represent an important set of species for testing the social complexity hypothesis for vocal communication--the notion that as groups increase in social complexity, there is a need for increased vocal complexity. Here, we describe the hypothesis and some of the early evidence that supported the hypothesis. Next, we review literature on social complexity and on vocal complexity in parids, and describe some of the studies that have made explicit tests of the social complexity hypothesis in one parid--Carolina chickadees, Poecile carolinensis. We conclude with a discussion, primarily from a parid perspective, of the benefits and costs of grouping and of physiological factors that might mediate the relationship between social complexity and changes in signalli...
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Papers by Cecilia Kullberg