Relative forelimb–hindlimb investment is associated with flight style, foraging strategy, and nestling period, but not nest type

We investigated Dial’s 2003 hypothesis that birds that rely more heavily on flight as their primary mode of locomotion and thus invest more in their forelimbs than hindlimbs will experience selection for smaller body sizes, greater altriciality, and more complex nests. To test this hypothesis, we examined the skeletons of over 2,000 individuals from 313 species representing the majority of avian families and all major branches of the avian tree. We used the lengths of the sternal keel and long bones of the wing relative to the lengths of the leg long bones as an index of relative locomotor investment. We found that locomotor investment was predicted by flight style, foraging method, and length of nestling period, supporting Dial’s hypothesis. Soaring birds and birds with more acrobatic flight styles, birds whose foraging methods were heavily reliant upon flight, and birds whose young spent more time in the nest tended to invest more in their forelimbs relative to hindlimbs. Nest type and body size were not significant predictors of relative forelimb–hindlimb investment, however, suggesting that the relationships among flight style, locomotor investment, and life history are not as tightly intertwined as Dial originally hypothesized.

Can agroecological management increase functional diversity of birds in rice fields?

Introduction: Recognition of the variety of ecosystem services that biodiversity performs in agroecosystems is one of the basic principles of agroecology. Because indices of functional diversity may be directly related with ecosystem services, an assessment of functional diversity can be useful for evaluating ecosystem services provided under agroecological management. Objective: We compared functional diversity of birds found in rice fields under conventional and agroecological management in the rice zone of Santa Fe Province, Argentina. Our objective was to determine whether agroecological management of rice is associated with a higher functional diversity and a different functional composition of birds than conventional management. Methods: We surveyed birds eight times, roughly every 15 days between November 2017 and March 2018, from beginning of sowing to before harvest, in both types of rice fields. Birds were sampled by a combined technique of line transects and point counts at four sites in each type of management. We calculated indices of functional diversity and composition based on morphologic and trophic attributes of birds detected in each type of field. Results: Functional richness, divergence and dispersion were higher under agroecological management. Only differences in functional richness between managements reflected differences in species richness. Community-level weighted means of trait values by sample varied between management types. An insectivorous diet, pursuit as a foraging method, and air and shrubs as foraging substrates were traits best represented under agroecological management. Conclusions: Our results suggest that agroecological management of rice crops is related with a higher functional diversity of birds than conventional practices, suggesting that agroecological management may enhance the provision of ecosystem services by birds in rice agroecosystems.

Combined effects of migration distance, foraging method vegetation density, and population density on wing shapes of boreal songbirds

In birds, migration distance is known to influence morphological attributes that influence flight performance, especially wing shape. However, wing shape is under the likely influence of less documented factors such as foraging method, vegetation density and isolation of individuals and populations. To better understand factors leading to interspecific differences in wing shape, we measured the pointedness of wings (Kipp’s distance) of 1017 live birds of 22 species in an eastern Canadian boreal forest. We modeled wing pointedness as a function of migration distances from eBird records, foraging, habitat, and population density data fromBirds of North Americamonographs. Long-distance migrants and species living in low-density vegetation had more pointed wings than shorter-distance migrants and dense-vegetation dwellers, in accordance to our predictions. After accounting for vegetation density and migration distance, we found no link between the extent of aerial foraging or mean breeding population density, an indicator of isolation, and wing pointedness. Those results are consistent with a tradeoff between sustained flight efficiency and maneuverability, but suggest that interspecific variation in wing shape due specifically to foraging method or habitat isolation is nonexistent or obscured by other factors.

Foundations of cumulative culture in apes: improved foraging efficiency through relinquishing and combining witnessed behaviors in chimpanzees (Pan troglodytes)

Evidence for culture in non-human species continues to grow, yet there are few candidate examples of cumulative culture outside of humans’ distinctively complex achievements. Prerequisites for cumulative culture include not only the ability to build on established behaviors but also to relinquish old ones and flexibly switch to more productive or efficient alternatives. Here, we established an inefficient solution to a foraging task in five groups of captive adult chimpanzees (N=19 - 4 male, 15 female; average group size of 8 individuals) living at the Michale E. Keeling Center for Comparative Medicine and Research. Three groups were subsequently seeded with a conspecific model who demonstrated an alternative, more efficient, solution to the same task. When participants could still successfully forage with their previously established behaviors, the majority of individuals did not switch to this more efficient solution; however, when their foraging method eventually became highly inefficient relative to that of the available alternative, nine chimpanzees with socially-acquired information (four of whom were exposed to additional human demonstrations) relinquished their old behaviors in favor of the more efficient one. In contrast, only one individual in a control group that did not witness a knowledgeable model was seen to do this (One-tailed Fisher’s exact test, p<.01). Individuals who switched were later able to combine behavioral components of these two techniques to produce a more efficient solution than their extensively used original extractive method (One-tailed Wilcoxon signed-rank test: Z = -2.410, N = 10, p < .01, r = -0.54). This suggests that the ability to combine independent behaviors to produce a superior compound technique, thought to be a major driving force of cultural evolution in hominin history, may have been inherited from an ancient ancestor shared with chimpanzees.

Foundations of cumulative culture in apes: improved foraging efficiency through relinquishing and combining witnessed behaviors in chimpanzees (Pan troglodytes)

Evidence for culture in non-human species continues to grow, yet there are few candidate examples of cumulative culture outside of humans’ distinctively complex achievements. Prerequisites for cumulative culture include not only the ability to build on established behaviors but also to relinquish old ones and flexibly switch to more productive or efficient alternatives. Here, we established an inefficient solution to a foraging task in five groups of captive adult chimpanzees (N=19 - 4 male, 15 female; average group size of 8 individuals) living at the Michale E. Keeling Center for Comparative Medicine and Research. Three groups were subsequently seeded with a conspecific model who demonstrated an alternative, more efficient, solution to the same task. When participants could still successfully forage with their previously established behaviors, the majority of individuals did not switch to this more efficient solution; however, when their foraging method eventually became highly inefficient relative to that of the available alternative, nine chimpanzees with socially-acquired information (four of whom were exposed to additional human demonstrations) relinquished their old behaviors in favor of the more efficient one. In contrast, only one individual in a control group that did not witness a knowledgeable model was seen to do this (One-tailed Fisher’s exact test, p<.01). Individuals who switched were later able to combine behavioral components of these two techniques to produce a more efficient solution than their extensively used original extractive method (One-tailed Wilcoxon signed-rank test: Z = -2.410, N = 10, p < .01, r = -0.54). This suggests that the ability to combine independent behaviors to produce a superior compound technique, thought to be a major driving force of cultural evolution in hominin history, may have been inherited from an ancient ancestor shared with chimpanzees.

Frugivory by birds on Schefflera morototoni (Araliaceae) in a Cerrado-Amazon orest transition area, eastern Mato Grosso, Brazil

Schefflera morototoni fruits are important food source for neotropical frugivorous birds. The objectives of the present study were to record bird species that consumed fruits of S. morototoni in a forest in the transition Cerrado-Amazon Forest, Mato Grosso, Brazil and evaluate the potential of these bird species as seed dispersers of this plant species. During 31 observation hours, from November 1 to 5, 2011, 23 bird species were recorded consuming S. morototoni fruits. Out of these, 20 bird species were considered potential seed dispersers, as they swallow the fruits whole. The species consuming the greatest number of fruits were Aburria cujubi (24% of total consumed fruits), Pteroglossus castanotis (18%), Tangara palmarum (12%), Patagioenas speciosa (11%), Ramphastos toco (8%), and Dacnis lineata (5%). The species T. palmarum showed the highest visit frequency (VF = 1.51), followed by P. castanotis (VF = 0.80), and D. lineata (VF = 0.77). All bird species employed picking foraging method for removal of fruits and in 11 species (48%) this method was the only one used. Agonistic interactions represented 13% of the total number of visits. Dacnis lineata received the highest number of attacks and P. castanotis and Pitangus sulphuratus were the more aggressive species. The high bird richness and the great number of consumed fruits indicated that the fruits of S. morototoni may be an important food resource for birds in the Cerrado-Amazon Forest transition

Evolution of host use, group-living and foraging behaviours in kleptoparasitic spiders: molecular phylogeny of the Argyrodinae (Araneae : Theridiidae)

Spiders in the subfamily Argyrodinae are known for their associations with other spiders. These associations include predation (araneophagy), web usurpation and kleptoparasitism. Although the majority of the 239 described species are solitary, ~20 species live in groups in the webs of their hosts. We constructed a molecular phylogeny of argyrodine genera and species in order to investigate (1) the evolution of araneophagy and kleptoparasitism, and (2) group-living and its association with particular types of host webs. We investigated the phylogeny of 41 primarily Asian and American species representing six recognised genera of Argyrodinae, using sequences of four genes: mitochondrial cytochrome c oxidase I (COI) and 16S rRNA (16S); and nuclear 28S rRNA (28S) and histone 3 (H3). We used Bayesian methods to reconstruct the ancestral states of three behavioural characters: foraging method, group-living and specialisation on large webs of large hosts. We tested for correlated evolution of group-living behaviour and specialisation on large webs using reversible-jump Markov chain Monte Carlo methods. The molecular phylogenetic analyses support the monophyly of the Argyrodinae. Reconstruction of ancestral states shows the evolutionary pathway of web-invading behaviour in Argyrodinae is from araneophagy to kleptoparasitism, and then to group-living kleptoparasitism. We found the evolution of group-living behaviour is strongly correlated with specialisation on the use of large host webs, which provide a larger food resource than smaller webs.