Few textbooks on research methods offer more than a few words of advice on how to devise scientif... more Few textbooks on research methods offer more than a few words of advice on how to devise scientific hypotheses. Big data is conceived as a hypothesis-generator procedure, a disruptive analytical innovation that is reconfiguring ecological research. My theses are (a) the hypotheses that big-data can originate "stricto sensu" are empirical generalizations that do not provide ecological understanding, (b) empirical generalizations may encourage instrumentalist research, but cannot supply ecological explanation, and (c) generalizations emerging from data-driven research can serve as a problem-generating procedure if they are reflected in the context of the theoretical framework surrounding the research. Discovery (e.g., novel patterns shown by big-data analysis) and invention (e.g., hypotheses on mechanisms and processes conjectured by the human mind) are complementary tools in ecological research because they play different epistemological roles. Data-driven research provides a useful analytical tool, but it does not justify any epistemological or methodological paradigm shift.
In this review, we compiled published results on biological interactions at different spatial sca... more In this review, we compiled published results on biological interactions at different spatial scales in the Monte desert of Argentina and identified gaps in current knowledge. We presented evidence of competitive and facilitative plant-plant conspecific and heterospecific interactions, and plant-soilmicrobes interactions in relation to the abiotic environment at the fine patch-scale. We also showed evidence of animal-animal interactions and plant-animal interactions at the community scale through study cases involving both native and introduced herbivores. Moreover, we identified bottom-up and top-down forces governing the interactions between granivores (birds, ants, and small mammals) and seed availability/production at the community scale. At the landscape scale, we discussed feedbacks between domestic grazers and the spatial patterns of resources and their interrelationships with processes occurring at other scales. We concluded that research has steadily increased during the last 6 years but knowledge on biological interactions in the Monte desert is still scarce, particularly at a landscape scale.
Science, technology, and professions form a system with strong interactions. Yet, these activitie... more Science, technology, and professions form a system with strong interactions. Yet, these activities attack different kinds of problems which require different kinds of solutions. The problems that trigger scientific and technological research remain insufficiently solved or unsolved, therefore their possible solutions must be invented (i.e. they are partially or totally original) and, consequently, they should be tested against reality by researchers before considering them as true or useful. On the contrary, the problems that trigger professional inquiry are already solved, or have at least some partial solution at hand that is available in the form of a technical protocol. This solution is applied with caution but without testing (i.e. the professional assumes that the solution works because it was already challenged by researchers). Moreover, science and technology tackle unsolved inverse problems, which allow the radical advancement of knowledge, and genuine innovation. A science policy based on a clear distinction between creative and routine activities (i.e. a creatively friendly policy) offers an opportunity for societies to reach value-added innovative economic and integral development. Résumé-La science, la technologie et les professions forment un système de fortes interactions. Pourtant, ces activités s'attaquent à différents types de problèmes qui nécessitent différentes solutions. Les problèmes qui aiguillonnent la recherche 1 Luis Marone earned his degree at the Universidad de La Plata, Argentina, in 1983, and his doctorate at the Universidad de San Luis, Argentina, in 1990, both in biological sciences. He has been a visiting professor at Argentinian universities
Las ideas de cambio evolutivo y de selección natural fueron dos contribuciones extraordinarias de... more Las ideas de cambio evolutivo y de selección natural fueron dos contribuciones extraordinarias de la ciencia del siglo XIX; Charles Darwin formalizó la primera sobre la base de algunos antecedentes notables e inventó la segunda, pero fue reticente a publicarlas en forma temprana. Ciertas afirmaciones del propio Darwin generaron la impresión de que, tras su retorno del viaje del Beagle, permaneció registrando y ordenando datos y realizando nuevas observaciones en búsqueda de una explicación (mecanismo causal) del cambio evolutivo. Ese relato podría no ajustarse a los hechos porque Darwin parece haber concebido sus ideas tempranamente, tal vez antes de 1840, aunque permaneció elaborándolas durante años. Su pretensión era publicarlas una vez que la evidencia en su favor fuera indudable. Temeroso de la opinión crítica de colegas y legos, Darwin examinó su teoría detalladamente, poniendo en evidencia sus supuestos más restrictivos y deduciendo “observaciones esperadas” en diversos escena...
Ecologists have abandoned attempts to develop a simple, unifying theory to account for community ... more Ecologists have abandoned attempts to develop a simple, unifying theory to account for community patterns (Lawton 1999). Instead, to explain such patterns, they rely on local ecological processes as well as on more contingent historical processes acting at large temporal and spatial scales (e.g., unique historical events controlling speciation and biogeographic interchanges). This mixed approach should lead to a more realistic idea of the real world, but it deserves careful epistemologicalconsideration. Although historical hypotheses may account for a substantial part of community patterns, they impose limits to theory development because they deal with contingent events that may often be theoretically intractable. An ecological system may be unique, but this does not necessarily imply that it is lawless in the ontological sense.
La science, la technologie et les professions forment un systeme de fortes interactions. Pourtant... more La science, la technologie et les professions forment un systeme de fortes interactions. Pourtant, ces activites s’attaquent a differents types de problemes qui necessitent differentes solutions. Les problemes qui aiguillonnent la recherche scientifique et technologique demeurent insuffisamment resolus ou non resolus, donc leurs possibles solutions doivent etre inventees (c.-a-d. qu’elles sont partiellement ou totalement originales) et, par consequent, elles doivent etre testees contre la realite par les chercheurs avant de les considerer comme vraies ou utiles. Par contre, les problemes qui aiguillonnent une investigation professionnelle sont deja resolus ou une solution partielle est disponible sous la forme d’un protocole technique. Cette solution est appliquee avec prudence sans etre testee (c’est-a-dire que le professionnel suppose que la solution fonctionne parce qu’elle a deja ete mise a l’epreuve par les chercheurs). De plus, la science et la technologie s’attaquent a des pr...
Protagonists of this story are citizens who had the privilege, after much effort, to get specific... more Protagonists of this story are citizens who had the privilege, after much effort, to get specific education becoming Geoscientists or Natural Scientists in general. They can act in three different spheres: doing science, developing technology, or applying as professionals the knowledge developed on the first two spheres [1]. Each sphere has different ways of generating, developing and applying knowledge. The main goal of science is to know, and the new knowledge acquired is an ‘intellectual artefact’. This artefact is the result of solving unknown problems by formulating and testing original hypothesis which, when proved, may be expressed in the form of laws or principles that aim to be the more general and perhaps deep scientific truths. When Geoscientists act at the technological sphere, their main goal is to propose or engineer original ‘technological artefacts’ in the form of devices, protocols of actions and/or processes, as a machine to produce electricity from new sources, or...
Las ideas de cambio evolutivo y de seleccion natural fueron dos contribuciones extraordinarias de... more Las ideas de cambio evolutivo y de seleccion natural fueron dos contribuciones extraordinarias de la ciencia del siglo XIX; Charles Darwin formalizo la primera sobre la base de algunos antecedentes notables e invento la segunda, pero fue reticente a publicarlas en forma temprana. Ciertas afirmaciones del propio Darwin generaron la impresion de que, tras su retorno del viaje del Beagle, permanecio registrando y ordenando datos y realizando nuevas observaciones en busqueda de una explicacion (mecanismo causal) del cambio evolutivo. Ese relato podria no ajustarse a los hechos porque Darwin parece haber concebido sus ideas tempranamente, tal vez antes de 1840, aunque permanecio elaborandolas durante anos. Su pretension era publicarlas una vez que la evidencia en su favor fuera indudable. Temeroso de la opinion critica de colegas y legos, Darwin examino su teoria detalladamente, poniendo en evidencia sus supuestos mas restrictivos y deduciendo “observaciones esperadas” en diversos escena...
Long-term field studies help unveil mechanisms of grass soil seed bank (SSB) persistence and resi... more Long-term field studies help unveil mechanisms of grass soil seed bank (SSB) persistence and resilience. We wonder whether grazing is a disruptive force that changes grass SSB composition and size, while heavy rainfall is a positive bottom-up force that restores the grass SSB in grazed areas of the Monte desert, Argentina. We used core sampling to study the grass SSB in cattle-free (17 year) and grazed (10 year) grasslands. The SSB size in cattle-free sites usually responded in a continuous positive fashion to rainfall, and the proportion of palatable grasses in the SSB was similar among years. Most grass species formed a transient SSB, but the presence of a stand of perennial plants would prevent their local extinction. In contrast, the SSB size in the grazed habitats showed a threshold response to rainfall (i.e. it did not increase under low-moderate rainfall), the seeds of palatable grasses were always scarce, and the proportion of seeds of less palatable grasses increased under extreme rainy conditions. Seed production from grasses that grew tillers from axillary buds during a drought was zero, suggesting that the bank of plants could have a role in the replenishment of the grass SSB only in mesic years. Within the time span assessed here, continuous heavy grazing together with scarce as well as heavy rainfall were disruptive forces that reduced the number and proportion of seeds from palatable grasses in the SSB, which are also the species preferred by seed-eating animals.
Numerical responses of animals to habitat perturbation often seem inconsistent, spreading skeptic... more Numerical responses of animals to habitat perturbation often seem inconsistent, spreading skepticism about the predictive capacity of applied ecology. Domestic grazing changes several habitat variables that can affect seedeating birds. Birds, in turn, show adaptations (e.g. in their feeding behavior) that could allow them to overcome habitat perturbations. Here we modelled habitat variables (e.g. cover of different plants, panicles, soil seed bank) in grazed and ungrazed (or lightly grazed) habitats of the central Monte desert, Argentina, to detect those affected by grazing activity. There was no effect of grazing on shrub and tree cover, but grazing reduced the abundance mostly of large grass seeds but also of small grass and forb seeds. Then, we used model's outputs and knowledge of feeding preferences of the five most common seed-eating passerines in the Monte to make speciesspecific predictions: changes in abundance of grass seed specialists (Saltatricula multicolor, Microspingus torquatus and Porphyrospiza carbonaria) due to grazing activity should be consistent and should depend on large grass seeds (i.e. preferred seeds), whereas changes in abundance of more generalist species (Zonotrichia capensis and Diuca diuca) should be less consistent and explained also by the abundance of other seeds. The abundance of large grass seeds was sufficient to predict the abundances of S. multicolor, M. torquatus and P. carbonaria. The best model for predicting the abundance of Z. capensis included large grass seeds as well as small grass or forb seeds. No model including the abundance of seeds predicted the abundance of D. diuca. Therefore, feeding behavior explained the abundance of four out of the five bird species. A review of the literature showed that feeding behavior is also a good predictor of habitat use in other desert grasslands. Conservative range management should consider, and even manipulate, the level of the seeds preferred by wildlife. Grazed grasslands should be rested from grazing on a rotational basis so that grasses, especially those whose seeds are preferred by birds, can seed.
Animal populations often decline due to habitat disturbance, but the initial response of organism... more Animal populations often decline due to habitat disturbance, but the initial response of organisms to human-induced environmental change is usually behavioral. Intra- and inter-specific interactions can restrict or facilitate access to resources, resulting in changes to individual fitness, and resource depletion may affect the frequency and strength of interactions. In birds, it is often assumed that feeding in groups increases foraging efficiency. We assessed how the reduction of seed resources provoked by cattle grazing affected different properties of seed-eating bird flocks in woodlands having the same structural characteristics but differing in seed abundance. Under lower availability of grass seeds (i.e., under grazing), flocks were smaller and less rich and birds showed a lower flocking propensity. This pattern could be explained by three non-exclusive hypotheses. Food reduction caused by grazing (i) decreases the number of seed-eating birds and concomitantly generates smalle...
Although bird population declines associated with land degradation are common, the initial respon... more Although bird population declines associated with land degradation are common, the initial response of organisms to rapid human-induced environmental change is usually behavioral. Reductions in seed availability due to cattle grazing may trigger diet switching in seed-eating birds, but empirical examples of such behavior are lacking. We asked whether cattle grazing changed the composition and reduced the size of seed reserves, and whether seed shortage caused diet shifts in 4 species of seed-eating birds wintering in the central Monte Desert, Argentina. We assessed the soil seed bank composition and the granivorous fraction of each species' diet. Digestive tract or crop contents were obtained by using the flushing method on individuals captured with mist nets, and seeds were sorted and assigned to 1 of 3 functional groups (small grass seeds, large and medium-sized grass seeds, or forb seeds). Cattle grazing reduced the abundance of the preferred large and medium-sized grass seeds by 60-90%. The grass-seed specialists Manycolored Chaco Finch (Saltatricula multicolor) and Ringed Warbling-Finch (Microspingus torquatus) did not change their diets in grazed areas, but the expanding specialists Common Diuca-Finch (Diuca diuca) and Rufous-collared Sparrow (Zonotrichia capensis) incorporated increased proportions of small grass seeds as well as forb seeds into their diets. These results were correctly predicted from species-specific differences in feeding flexibility previously established in cafeteria experiments. Based on species-specific diet composition, the energy reward of seeds by unit mass consumed decreased moderately (5-21%) in the grazed sites for S. multicolor, M. torquatus, and D. diuca. Starch content was similar between grazing conditions for all 3 birds. Although such deficits might be compensated for by a slight increase in absolute mass of seeds or alternative food items consumed in degraded lands, substantial reduction in the availability of grass seeds may reduce the capacity of degraded lands to support specialist granivorous birds.
Few textbooks on research methods offer more than a few words of advice on how to devise scientif... more Few textbooks on research methods offer more than a few words of advice on how to devise scientific hypotheses. Big data is conceived as a hypothesis-generator procedure, a disruptive analytical innovation that is reconfiguring ecological research. My theses are (a) the hypotheses that big-data can originate "stricto sensu" are empirical generalizations that do not provide ecological understanding, (b) empirical generalizations may encourage instrumentalist research, but cannot supply ecological explanation, and (c) generalizations emerging from data-driven research can serve as a problem-generating procedure if they are reflected in the context of the theoretical framework surrounding the research. Discovery (e.g., novel patterns shown by big-data analysis) and invention (e.g., hypotheses on mechanisms and processes conjectured by the human mind) are complementary tools in ecological research because they play different epistemological roles. Data-driven research provides a useful analytical tool, but it does not justify any epistemological or methodological paradigm shift.
In this review, we compiled published results on biological interactions at different spatial sca... more In this review, we compiled published results on biological interactions at different spatial scales in the Monte desert of Argentina and identified gaps in current knowledge. We presented evidence of competitive and facilitative plant-plant conspecific and heterospecific interactions, and plant-soilmicrobes interactions in relation to the abiotic environment at the fine patch-scale. We also showed evidence of animal-animal interactions and plant-animal interactions at the community scale through study cases involving both native and introduced herbivores. Moreover, we identified bottom-up and top-down forces governing the interactions between granivores (birds, ants, and small mammals) and seed availability/production at the community scale. At the landscape scale, we discussed feedbacks between domestic grazers and the spatial patterns of resources and their interrelationships with processes occurring at other scales. We concluded that research has steadily increased during the last 6 years but knowledge on biological interactions in the Monte desert is still scarce, particularly at a landscape scale.
Science, technology, and professions form a system with strong interactions. Yet, these activitie... more Science, technology, and professions form a system with strong interactions. Yet, these activities attack different kinds of problems which require different kinds of solutions. The problems that trigger scientific and technological research remain insufficiently solved or unsolved, therefore their possible solutions must be invented (i.e. they are partially or totally original) and, consequently, they should be tested against reality by researchers before considering them as true or useful. On the contrary, the problems that trigger professional inquiry are already solved, or have at least some partial solution at hand that is available in the form of a technical protocol. This solution is applied with caution but without testing (i.e. the professional assumes that the solution works because it was already challenged by researchers). Moreover, science and technology tackle unsolved inverse problems, which allow the radical advancement of knowledge, and genuine innovation. A science policy based on a clear distinction between creative and routine activities (i.e. a creatively friendly policy) offers an opportunity for societies to reach value-added innovative economic and integral development. Résumé-La science, la technologie et les professions forment un système de fortes interactions. Pourtant, ces activités s'attaquent à différents types de problèmes qui nécessitent différentes solutions. Les problèmes qui aiguillonnent la recherche 1 Luis Marone earned his degree at the Universidad de La Plata, Argentina, in 1983, and his doctorate at the Universidad de San Luis, Argentina, in 1990, both in biological sciences. He has been a visiting professor at Argentinian universities
Las ideas de cambio evolutivo y de selección natural fueron dos contribuciones extraordinarias de... more Las ideas de cambio evolutivo y de selección natural fueron dos contribuciones extraordinarias de la ciencia del siglo XIX; Charles Darwin formalizó la primera sobre la base de algunos antecedentes notables e inventó la segunda, pero fue reticente a publicarlas en forma temprana. Ciertas afirmaciones del propio Darwin generaron la impresión de que, tras su retorno del viaje del Beagle, permaneció registrando y ordenando datos y realizando nuevas observaciones en búsqueda de una explicación (mecanismo causal) del cambio evolutivo. Ese relato podría no ajustarse a los hechos porque Darwin parece haber concebido sus ideas tempranamente, tal vez antes de 1840, aunque permaneció elaborándolas durante años. Su pretensión era publicarlas una vez que la evidencia en su favor fuera indudable. Temeroso de la opinión crítica de colegas y legos, Darwin examinó su teoría detalladamente, poniendo en evidencia sus supuestos más restrictivos y deduciendo “observaciones esperadas” en diversos escena...
Ecologists have abandoned attempts to develop a simple, unifying theory to account for community ... more Ecologists have abandoned attempts to develop a simple, unifying theory to account for community patterns (Lawton 1999). Instead, to explain such patterns, they rely on local ecological processes as well as on more contingent historical processes acting at large temporal and spatial scales (e.g., unique historical events controlling speciation and biogeographic interchanges). This mixed approach should lead to a more realistic idea of the real world, but it deserves careful epistemologicalconsideration. Although historical hypotheses may account for a substantial part of community patterns, they impose limits to theory development because they deal with contingent events that may often be theoretically intractable. An ecological system may be unique, but this does not necessarily imply that it is lawless in the ontological sense.
La science, la technologie et les professions forment un systeme de fortes interactions. Pourtant... more La science, la technologie et les professions forment un systeme de fortes interactions. Pourtant, ces activites s’attaquent a differents types de problemes qui necessitent differentes solutions. Les problemes qui aiguillonnent la recherche scientifique et technologique demeurent insuffisamment resolus ou non resolus, donc leurs possibles solutions doivent etre inventees (c.-a-d. qu’elles sont partiellement ou totalement originales) et, par consequent, elles doivent etre testees contre la realite par les chercheurs avant de les considerer comme vraies ou utiles. Par contre, les problemes qui aiguillonnent une investigation professionnelle sont deja resolus ou une solution partielle est disponible sous la forme d’un protocole technique. Cette solution est appliquee avec prudence sans etre testee (c’est-a-dire que le professionnel suppose que la solution fonctionne parce qu’elle a deja ete mise a l’epreuve par les chercheurs). De plus, la science et la technologie s’attaquent a des pr...
Protagonists of this story are citizens who had the privilege, after much effort, to get specific... more Protagonists of this story are citizens who had the privilege, after much effort, to get specific education becoming Geoscientists or Natural Scientists in general. They can act in three different spheres: doing science, developing technology, or applying as professionals the knowledge developed on the first two spheres [1]. Each sphere has different ways of generating, developing and applying knowledge. The main goal of science is to know, and the new knowledge acquired is an ‘intellectual artefact’. This artefact is the result of solving unknown problems by formulating and testing original hypothesis which, when proved, may be expressed in the form of laws or principles that aim to be the more general and perhaps deep scientific truths. When Geoscientists act at the technological sphere, their main goal is to propose or engineer original ‘technological artefacts’ in the form of devices, protocols of actions and/or processes, as a machine to produce electricity from new sources, or...
Las ideas de cambio evolutivo y de seleccion natural fueron dos contribuciones extraordinarias de... more Las ideas de cambio evolutivo y de seleccion natural fueron dos contribuciones extraordinarias de la ciencia del siglo XIX; Charles Darwin formalizo la primera sobre la base de algunos antecedentes notables e invento la segunda, pero fue reticente a publicarlas en forma temprana. Ciertas afirmaciones del propio Darwin generaron la impresion de que, tras su retorno del viaje del Beagle, permanecio registrando y ordenando datos y realizando nuevas observaciones en busqueda de una explicacion (mecanismo causal) del cambio evolutivo. Ese relato podria no ajustarse a los hechos porque Darwin parece haber concebido sus ideas tempranamente, tal vez antes de 1840, aunque permanecio elaborandolas durante anos. Su pretension era publicarlas una vez que la evidencia en su favor fuera indudable. Temeroso de la opinion critica de colegas y legos, Darwin examino su teoria detalladamente, poniendo en evidencia sus supuestos mas restrictivos y deduciendo “observaciones esperadas” en diversos escena...
Long-term field studies help unveil mechanisms of grass soil seed bank (SSB) persistence and resi... more Long-term field studies help unveil mechanisms of grass soil seed bank (SSB) persistence and resilience. We wonder whether grazing is a disruptive force that changes grass SSB composition and size, while heavy rainfall is a positive bottom-up force that restores the grass SSB in grazed areas of the Monte desert, Argentina. We used core sampling to study the grass SSB in cattle-free (17 year) and grazed (10 year) grasslands. The SSB size in cattle-free sites usually responded in a continuous positive fashion to rainfall, and the proportion of palatable grasses in the SSB was similar among years. Most grass species formed a transient SSB, but the presence of a stand of perennial plants would prevent their local extinction. In contrast, the SSB size in the grazed habitats showed a threshold response to rainfall (i.e. it did not increase under low-moderate rainfall), the seeds of palatable grasses were always scarce, and the proportion of seeds of less palatable grasses increased under extreme rainy conditions. Seed production from grasses that grew tillers from axillary buds during a drought was zero, suggesting that the bank of plants could have a role in the replenishment of the grass SSB only in mesic years. Within the time span assessed here, continuous heavy grazing together with scarce as well as heavy rainfall were disruptive forces that reduced the number and proportion of seeds from palatable grasses in the SSB, which are also the species preferred by seed-eating animals.
Numerical responses of animals to habitat perturbation often seem inconsistent, spreading skeptic... more Numerical responses of animals to habitat perturbation often seem inconsistent, spreading skepticism about the predictive capacity of applied ecology. Domestic grazing changes several habitat variables that can affect seedeating birds. Birds, in turn, show adaptations (e.g. in their feeding behavior) that could allow them to overcome habitat perturbations. Here we modelled habitat variables (e.g. cover of different plants, panicles, soil seed bank) in grazed and ungrazed (or lightly grazed) habitats of the central Monte desert, Argentina, to detect those affected by grazing activity. There was no effect of grazing on shrub and tree cover, but grazing reduced the abundance mostly of large grass seeds but also of small grass and forb seeds. Then, we used model's outputs and knowledge of feeding preferences of the five most common seed-eating passerines in the Monte to make speciesspecific predictions: changes in abundance of grass seed specialists (Saltatricula multicolor, Microspingus torquatus and Porphyrospiza carbonaria) due to grazing activity should be consistent and should depend on large grass seeds (i.e. preferred seeds), whereas changes in abundance of more generalist species (Zonotrichia capensis and Diuca diuca) should be less consistent and explained also by the abundance of other seeds. The abundance of large grass seeds was sufficient to predict the abundances of S. multicolor, M. torquatus and P. carbonaria. The best model for predicting the abundance of Z. capensis included large grass seeds as well as small grass or forb seeds. No model including the abundance of seeds predicted the abundance of D. diuca. Therefore, feeding behavior explained the abundance of four out of the five bird species. A review of the literature showed that feeding behavior is also a good predictor of habitat use in other desert grasslands. Conservative range management should consider, and even manipulate, the level of the seeds preferred by wildlife. Grazed grasslands should be rested from grazing on a rotational basis so that grasses, especially those whose seeds are preferred by birds, can seed.
Animal populations often decline due to habitat disturbance, but the initial response of organism... more Animal populations often decline due to habitat disturbance, but the initial response of organisms to human-induced environmental change is usually behavioral. Intra- and inter-specific interactions can restrict or facilitate access to resources, resulting in changes to individual fitness, and resource depletion may affect the frequency and strength of interactions. In birds, it is often assumed that feeding in groups increases foraging efficiency. We assessed how the reduction of seed resources provoked by cattle grazing affected different properties of seed-eating bird flocks in woodlands having the same structural characteristics but differing in seed abundance. Under lower availability of grass seeds (i.e., under grazing), flocks were smaller and less rich and birds showed a lower flocking propensity. This pattern could be explained by three non-exclusive hypotheses. Food reduction caused by grazing (i) decreases the number of seed-eating birds and concomitantly generates smalle...
Although bird population declines associated with land degradation are common, the initial respon... more Although bird population declines associated with land degradation are common, the initial response of organisms to rapid human-induced environmental change is usually behavioral. Reductions in seed availability due to cattle grazing may trigger diet switching in seed-eating birds, but empirical examples of such behavior are lacking. We asked whether cattle grazing changed the composition and reduced the size of seed reserves, and whether seed shortage caused diet shifts in 4 species of seed-eating birds wintering in the central Monte Desert, Argentina. We assessed the soil seed bank composition and the granivorous fraction of each species' diet. Digestive tract or crop contents were obtained by using the flushing method on individuals captured with mist nets, and seeds were sorted and assigned to 1 of 3 functional groups (small grass seeds, large and medium-sized grass seeds, or forb seeds). Cattle grazing reduced the abundance of the preferred large and medium-sized grass seeds by 60-90%. The grass-seed specialists Manycolored Chaco Finch (Saltatricula multicolor) and Ringed Warbling-Finch (Microspingus torquatus) did not change their diets in grazed areas, but the expanding specialists Common Diuca-Finch (Diuca diuca) and Rufous-collared Sparrow (Zonotrichia capensis) incorporated increased proportions of small grass seeds as well as forb seeds into their diets. These results were correctly predicted from species-specific differences in feeding flexibility previously established in cafeteria experiments. Based on species-specific diet composition, the energy reward of seeds by unit mass consumed decreased moderately (5-21%) in the grazed sites for S. multicolor, M. torquatus, and D. diuca. Starch content was similar between grazing conditions for all 3 birds. Although such deficits might be compensated for by a slight increase in absolute mass of seeds or alternative food items consumed in degraded lands, substantial reduction in the availability of grass seeds may reduce the capacity of degraded lands to support specialist granivorous birds.
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