Mechanical problem solving by plush-crested jays: are tools special after all?

Tool use is taxonomically associated with high behavioural flexibility and innovativeness, and its prevalence is greater in primates and some bird species. This association, however, is not known to be causally determinant of tool-related competence since flexibility and innovativeness are often observed in the absence of tool use and vice versa. For this reason, it is interesting to explore whether animals that can be loosely categorized as outstanding, or 'intelligent' physical problem solvers, are also remarkable using tools innovatively, rather than tool use presenting special constraints.

Sex differences in learning flexibility in an avian brood parasite, the shiny cowbird.

Females of brood parasitic shiny cowbirds, Molothrus bonariensis, search and prospect host nests, synchronizing parasitism with host laying. This behavior is sex-specific, as females perform this task without male's assistance. Host nests must be removed from the female's memory "library" after being parasitized, to avoid repeated parasitism, or when they become unavailable because of predation.

Sex differences in the use of spatial cues in two avian brood parasites.

Shiny and screaming cowbirds are avian interspecific brood parasites that locate and prospect host nests in daylight and return from one to several days later to lay an egg during the pre-dawn twilight. Thus, during nest location and prospecting, both location information and visual features are available, but the latter become less salient in the low-light conditions when the nests are visited for laying. This raises the question of how these different sources of information interact, and whether this reflects different behavioural specializations across sexes.

Female and male rufous horneros eject shiny cowbird eggs using a mental template of the size of their own eggs.

Hosts of interspecific brood parasites often evolve antiparasitic defences, like the recognition and rejection of parasite's eggs. Most hosts use differences in coloration and maculation to discriminate between their own and parasitic eggs, but there are a few cases of hosts using the size of eggs as a cue. To recognize parasite eggs, hosts may require the presence of their own eggs and use a discordancy rule or may use a mental template of their own eggs.

Molecular tracking of individual host use in the Shiny Cowbird - a generalist brood parasite.

Generalist parasites exploit multiple host species at the population level, but the individual parasite's strategy may be either itself a generalist or a specialist pattern of host species use. Here, we studied the relationship between host availability and host use in the individual parasitism patterns of the Shiny Cowbird Molothrus bonariensis, a generalist avian obligate brood parasite that parasitizes an extreme range of hosts. Using five microsatellite markers and an 1120-bp fragment of the mtDNA control region, we reconstructed full-sibling groups from 359 cowbird eggs and chicks found in nests of the two most frequent hosts in our study area, the Chalk-browed Mockingbird Mimus saturninus and the House Wren Troglodytes aedon.