The value of a mouthful: Flight initiation distance as an opportunity cost

Flight initiation distance of animals when approached by a potential predator reflects the risk that an individual is willing to take when the individual has to gauge the value of staying put relative to the cost of flight. I predicted that this cost–benefit balance would depend on the opportunity cost of fleeing. This opportunity cost can be estimated as the difference in flight initiation distance (FID) between an individual engaged in eating rather than just loafing. I estimated FID of 55 species of birds when approached by a human whilst eating or loafing. There was highly significant variation in difference in FID between these two situations amongst species. Species eating mobile food that is difficult to catch showed little difference in FID between the two situations, whilst species eating immobile food such as seeds had longer FID when eating than when loafing. This difference was fully attributed to differences in relative eye size, because species that had longer FIDs when foraging rather than loafing had small eyes, whilst species with long FIDs when loafing rather than foraging had large eyes. Species with long FIDs, when foraging compared to loafing, had low adult annual survival rates and vice versa. This effect was independent of whether mobile or immobile food was consumed. These findings suggest that individuals of different species adjust their FID to the probability of adult survival and also that differences in visual acuity among species as reflected by eye size linked to differences in food mobility affect the opportunity cost of risk taking

Concerns about the use of ecosystem services as a tool for nature conservation: From misleading concepts to providing a “price” for nature, but not a “value”

1. By definition, ecosystem services (ES) are the “benefits that people obtain from ecosystems”, and this paradigm has been increasingly used in recent decades in ecological planning, for policy development and environmental management.2. In this short commentary, we highlight the main criticisms suggested by several scientists against the currently used and abused ecosystem services (ES) approach.3. We underline how this concept needs a more accurate scientific assessment and theoretical development, repeating that one of the most critical concerns is that this paradigm assigns a “price”, but not a “value” to nature.4. We also discuss different theoretical concerns, as for example the replacement of natural “resource” by “service” promoted by the ES paradigm thereby changing the implications of such assessments. Conserving resources is essential for survival of several organisms, while conservation of a “service” is mainly related to the human species.5. Finally, we warn against the mechanism of ‘crowding out’ behind the ES approach, which replaces intrinsic motivations (nature) against extrinsic ones (benefits), highlighting that people do not need to attach different values to ecosystems (monetary, cultural, aesthetic, etc.) to understand the value of nature

Function of the uropygial gland in eiders (Somateria mollissima)

International audienceBackground: The uropygial gland is an exocrine gland located above the tail of birds that produces a diverse range of biochemicals. It has been hypothesized to be involved in chemical protection, water-proofing and maintenance of plumage brightness. Although these not necessarily mutually exclusive functions have received some empirical support , there has been little empirical research on the function of water-proofing. Methods: Here we analyzed data for 229 individual eiders (Somateria mollissima) collected by Danish hunters during 2016-2018. Results: The Eider is a sea-duck that spends almost its entire life in sea water emphasizing water-proofing of the plumage. The size of the uropygial gland increased with body mass in males, but not in females, and it increased with age. The size of the uropygial gland decreased during winter. Eiders with small uropygial glands grew their feathers at a fast rate. Eiders with large wing areas had large uropygial glands. Conclusions: These findings are consistent with large uropygial glands playing a role in water-proofing during molt and foraging, but also that uropygial glands may play a role in chemical defense

Large feet are beneficial for eiders Somateria mollissima

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Flight initiation distance, color and camouflage

International audienceCamouflage is widespread throughout the animal kingdom allowing individuals to avoid detection and hence save time and energy rather than escape from an approaching predator. Thus, camouflage is likely to have co-evolved with antipredator behavior. Here, we propose that camouflage results in dichotomous escape behavior within and among species with classes of individuals and species with cryptic coloration having shorter flight initiation distances (FIDs; the distance at which an individual takes flight when approached by a human). We report the results of 2 tests of this hypothesis. First, bird species with cryptically colored plumage have consistently shorter FID than closely related species without such color. Within species with sexually dimorphic plumage, brightly colored adult male common pheasants Phasianus colchicus and golden pheasants Chrysolophus pictus have long and variable FID, whereas cryptically colored juveniles and adult females have short and invariable FID. Second, FID in females was predicted by presence or absence of cryptic color, FID in males and their interaction. These findings are consistent with the hypothesis that risk-taking behavior has been attuned to camouflage, and that species with different levels of camouflage differ consistently in their FID

Using 3D modelling and printing to study avian cognition from different geometric dimensions

International audienceStudying animal cognition is meaningful because it helps us understand how animals adapt to the natural environment. Many birds build nests, clean their nests and reject foreign objects from their nests, which provide an optimal opportunity for studying their cognition toward foreign objects in nests. However, handmade models used in previous studies have many deficiencies that considerably constrain our capacity to understand the evolution of avian cognition of foreign objects because they are unquantifiable and dependent on different features. We established a 3D modelling and printing method to manipulate one geometric dimension of a model while controlling for others, which allowed us to investigate avian cognition for different dimensions independently. Here we introduce this method, conduct an empirical study as an example, and discuss its applications to further studies

Spatial heterogeneity in distribution and ecology of Western Palearctic birds

Copyright by the Ecological Society of AmericaSpecies vary in abundance and heterogeneity of spatial distribution, and the ecological and evolutionary consequences of such variability are poorly known. Evolutionary adaptation to heterogeneously distributed resources may arise from local adaptation with individuals of such locally adapted populations rarely dispersing long distances and hence having small populations and small overall ranges. We quantified mean population density and spatial heterogeneity in population density of 197 bird species across 12 similarly sized regions in the Western Palearctic. Variance in population density among regions differed significantly from a Poisson distribution, suggesting that random processes cannot explain the observed patterns. National estimates of means and variances in population density were positively correlated with continental estimates, suggesting that means and variances were maintained across spatial scales. We used Morisita's index of population abundance as an estimate of heterogeneity in distribution among regions to test a number of predictions. Heterogeneously distributed passerine bird species as reflected by Morisita's index had small populations, low population densities, and small breeding ranges. Their breeding populations had been consistently maintained at low levels for considerable periods of time, because the degree of genetic variation in a subsample of non-passerines and passerines was significantly negatively related to heterogeneity in distribution. Heterogeneously distributed passerine species were not more often habitat specialists than homogeneously distributed species. Furthermore, heterogeneously distributed passerine species had high annual adult survival rates but did not differ in annual fecundity from homogeneously distributed species. Heterogeneously distributed passerine species rarely colonized urban habitats. Finally, homogeneously distributed bird species were hosts to a greater diversity of blood parasite species than heterogeneously distributed species. In conclusion, small breeding ranges, population sizes, and population densities of heterogeneously distributed passerine bird species, combined with their low degree of genetic variability, and their inability to colonize urban areas may render such species particularly susceptible to human-influenced global climatic changes.The study received financial support from project CGL2007-61251/BOS-FEDER (to J. J. Soler and A. P. Møller) and Junta de Andalucía grants to research groups RNM 340 (to J. J. Soler) and RNM 341 (to M. M. Vivaldi).Peer reviewe

Geographic distribution of suitable hosts explains the evolution of specialized gentes in the European cuckoo Cuculus canorus

Background Several types of selective forces can act to promote parasite specialization. Parasites might specialize on some suitable hosts at the cost of decreasing effectiveness when exploiting other species of hosts, and specialization can be more easily selected for in hosts that the parasites will easily find. Thus demographic characteristics of suitable hosts such as population density and its spatial consistency could be key factors predicting probability of parasite specialization and speciation. Here, we explore this hypothesis by studying the relationship between occurence of specialized races of the European cuckoo (Cuculus canorus) (i.e. gentes) and mean and coefficient of variation in population density estimated for 12 different European regions. Results The results were in accordance with the hypothesis because specialized cuckoo egg morphs were more common in suitable hosts with high population density and low variation in population density at the level of host species or genera. Conclusion We have presented evidence suggesting that population density and homogeneity of geographic distribution of hosts explain, at least partly, the evolution of specialized egg-morphs of the European cuckoo. These results are consistent with the hypothesis that resource (i.e., host) predictability explains the evolution of host races and species of parasites.The study received financial support from project CGL2007-61251/BOS – FEDER to JJS and APM and Junta de Andalucía grants to research groups RNM 340 (JJS) and RNM 341 (MMV)

Multiple components of environmental change drive populations of breeding waders in seminatural grasslands

Environments are rapidly changing due to climate change, land use, intensive agriculture, and the impact of hunting on predator populations. Here, we analyzed longterm data recorded during 1928–2014 on the size of breeding populations of waders at two large nature reserves in Denmark, Vejlerne and Tipperne, to determine the effects of components of environmental change on breeding populations of waders. Environmental variables and counts of waders were temporally autocorrelated, and we used generalized least square (GLS) by incorporating the first-order autoregressive correlation structure in the analyses. We attempted to predict the abundance of waders for short-term trends for two nature reserves (35 years) and for long-term trends for one nature reserve (86 years), using precipitation, temperature, nutrients, abundance of foxes Vulpes vulpes, area grazed, and number of cattle. There was evidence of impacts of nutrients, climate (long-term changes in temperature and precipitation), grazing, mowing, and predation on bird populations. We used standard random effects meta-analyses weighted by (N–3) to quantify these mean effects. There was no significant difference in effect size among species, while mean effect size differed consistently among environmental factors, and the interaction between effect size for species and environmental factors was also significant. Thus, environmental factors affected the different species differently. Mean effect size was the largest at +0.20 for rain, +0.11 for temperature, −0.09 for fox abundance, and −0.03 for number of cattle, while there was no significant mean effect for fertilizer, area grazed, and year. Effect sizes for two short-term time series from Tipperne and Vejlerne were positively correlated as were effect sizes for short-term and long-term time series at Tipperne. This implies that environmental factors had consistent effects across large temporal and spatial scales