Allocation Of Parental Care Research Articles

The influence of geographical location, host maturity and sex on intestinal helminth communities of the double-crested cormorant Phalacrocorax auritus from the eastern United States.

Here the intestinal helminth infracommunities of 218 double-crested cormorants (Phalacrocorax auritus) from 11 locations in Alabama, Minnesota, Mississippi and Vermont are documented. Trematode infections were present in 98% of hosts; 65% of cormorants carried cestode infections, 4% were infected with acanthocephalans and 66% had nematode intestinal parasites. Parasite infracommunities of hosts collected on wintering grounds had higher richness and diversity than did birds collected on breeding grounds. Differences in parasite richness and diversity between male and female P. auritus were also detected, but not between immature and mature bird hosts. Parasite intensity did not differ by sex, maturity, or between breeding and wintering season. The most common parasite was Drepanocephalus auritus (spathans), which is recognized as a disease agent that negatively impacts the catfish aquaculture industry in the US. Echinochasmus sp. in double-crested cormorants is documented for the first time in the United States. We suggest that the differences observed among parasite infracommunities could be associated with the foraging distances travelled by P. auritus during breeding and wintering seasons, which is limited by allocation of parental care during the breeding season.

Cross-fostering reveals that among-brood differences in ornamental mouth coloration mostly reflect rearing conditions in nestling house sparrows

Dependent offspring use specialized traits to attract parental care. In birds, this includes morphological ornaments (e.g. colourful plumage or mouthparts) that are associated with nestling condition and shape the allocation of parental care. Ornament expression often differs among broods, even after differences in individual condition are accounted for statistically. Understanding how this variation arises is important for understanding the information content of these signals, their functional importance, and their evolution. The present study used a cross-fostering experiment to assess the relative contributions of parental effects to among-brood differences in the mouth coloration of nestling house sparrows, specifically the carotenoid-richness, overall brightness, and ultraviolet (UV) coloration of rictal flanges. The expression of carotenoid-based coloration was explained by synchronous breeding, nest-of-rearing and nest-of-origin. Brightness and relative UV intensity, however, were explained only by synchronous breeding, and there was substantial unexplained variation in all three colour parameters. Among-brood variation in mouth coloration, then, may primarily contain information about the environment in which offspring are reared. At the individual level, ontogenetic changes in the carotenoid-richness and brightness of flanges positively reflected mass gain (a proxy for food intake). Larger and yellower chicks gained more mass, consistent with parental preferences for these traits. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 169–179.

Post-fledging brood and care division in the roseate tern (Sterna dougallii)

Extended post-fledging parental care is an important aspect of parental care in birds, although little studied due to logistic difficulties. Commonly, the brood is split physically (brood division) and/or preferential care is given to a subset of the brood by one parent or the other (care division). Among gulls and tern (Laridae), males and females generally share parental activities during the pre-fledging period, but the allocation of parental care after fledging is little documented. This study examined the behaviour of male and female roseate terns (Sterna dougallii) during the late chick-rearing and early post-fledging periods, and in particular the amount of feeds and the time spent in attendance given to individual chicks/fledglings. Pre-fledging parental care was biparental in all cases. Post-fledging parental care was dependent on the number of fledglings in the brood. Males and females continued biparental care in clutches with one surviving fledgling, while in two-fledgling clutches, males fed the A-fledgling while females fed the B-fledgling. Overall, there was no difference in attendance, only in feeds. This division of care may be influenced by the male only being certain of the paternity of the A-chick but not by chick sex.

Consequences of variation in brood size on the allocation of parental care in common terns (Sterna hirundo)

Data on the behaviour of common tern (Sterna hirundo) parents were analyzed to document shifts in parental care patterns with changes in brood size. The primary roles of the sexes, chick feeding by males, and brood attendance by females, did not change with shifts in brood size. Rather, parents simply altered the amount of care provided. One-chick broods received more parental attendance at the nest site than both two- and three-chick broods, likely as a result of the increased foraging effort of two- and three-chick parents. The number of chick feeds per hour increased significantly with each increase in brood size, but the number of feeds of each chick per hour did not. Thus, although parents increased their foraging effort with increasing brood size, the net effect was that chicks in all brood sizes were fed at similar rates.