| differential reproductive success favours strong host preference in a highly specialized brood parasite. | obligate avian brood parasites show dramatic variation in the degree to which they are host specialists or host generalists. the screaming cowbird molothrus rufoaxillaris is one of the most specialized brood parasites, using a single host, the bay-winged cowbird (agelaioides badius) over most of its range. coevolutionary theory predicts increasing host specificity the longer the parasite interacts with a particular avian community, as hosts evolve defences that the parasite cannot counteract. ac ... | 2008 | 18647716 |
| new data on the taxonomy and distribution of ten neotropical chewing lice of the genus myrsidea (phthiraptera: menoponidae), including the description of a new species. | the new species myrsidea alexanderi is described and illustrated ex pheugopedius maculipectus (troglodytidae) from honduras. redescriptions and illustrations are given for both sexes of myrsidea chiapensis ex calocitta formosa from costa rica, and the male of m. dissimilis ex progne chalybea from brazil. also, seven other previously known species or subspecies of the louse genus myrsidea are recorded and discussed from passerine birds of the neotropical region, as follows: myrsidea antiqua, myrs ... | 2016 | 27394300 |
| distribution of substance p reveals a novel subdivision in the hippocampus of parasitic south american cowbirds. | parasitic cowbirds monitor potential hosts' nests and return to lay when appropriate, a task that is likely to involve spatial recall. seasonal and sexual behavioral variations in the cowbirds correlate with anatomical changes in the hippocampal formation. during the breeding season, parasites have larger hippocampal formations than nonparasites. in parasitic species in which females alone perform nest bookkeeping, females have larger hippocampal formations than males. we investigated the distri ... | 2006 | 16615130 |
| a novel method of rejection of brood parasitic eggs reduces parasitism intensity in a cowbird host. | the hosts of brood parasitic birds are under strong selection pressure to recognize and remove foreign eggs from their nests, but parasite eggs may be too large to be grasped whole and too strong to be readily pierced by the host's bill. such operating constraints on egg removal are proposed to force some hosts to accept parasite eggs, as the costs of deserting parasitized clutches can outweigh the cost of rearing parasites. by fitting microcameras inside nests, we reveal that the neotropical ba ... | 2013 | 23485877 |
| host-parasite coevolution beyond the nestling stage? mimicry of host fledglings by the specialist screaming cowbird. | egg mimicry by obligate avian brood parasites and host rejection of non-mimetic eggs are well-known textbook examples of host-parasite coevolution. by contrast, reciprocal adaptations and counteradaptations beyond the egg stage in brood parasites and their hosts have received less attention. the screaming cowbird (molothrus rufoaxillaris) is a specialist obligate brood parasite whose fledglings look identical to those of its primary host, the baywing (agelaioides badius). such a resemblance has ... | 2012 | 22648157 |
| sexual dimorphism and species differences in hvc volumes of cowbirds. | cowbirds exhibit extensive variation in their social, territorial, and reproductive behaviors. nissl-stained brain sections of specimens from a previous study (j. c. reboreda, n. s. clayton, & a. kacelnik, 1996) were used to study the gross anatomy of a song control nucleus in 3 south american cowbirds (bay-winged, molothrus badius; shiny, m. bonariensis; and screaming, m. rufoaxillaris). cowbird high vocal center (hvc) volumes were consistently higher in males than in females in all 3 species. ... | 1999 | 10571492 |
| species and sex differences in hippocampus size in parasitic and non-parasitic cowbirds. | to test the hypothesis that selection for spatial abilities which require birds to locate and to return accurately to host nests has produced an enlarged hippocampus in brood parasites, three species of cowbird were compared. in shiny cowbirds, females search for host nests without the assistance of the male; in screaming cowbirds, males and females inspect hosts' nests together; in bay-winged cowbirds, neither sex searches because this species is not a brood parasite. as predicted, the two para ... | 1996 | 8730816 |