The effects of urbanization on body condition and plumage condition in nestling and juvenile Florida scrub-jays

Background/Question/Methods

Urbanization can simultaneously increase and decrease resources for birds. Adults can benefit from anthropogenic foods, but nestlings, which require easily digestible protein-rich food, suffer from the reduced arthropod abundance associated with urbanization. Wildland Florida Scrub-Jay nestlings are fed exclusively arthropods, but anthropogenic foods are included in the suburban nestling diet. We compared the condition of nestling and juvenile Florida Scrub-Jays in both habitats using morphometrics, ptilochronology, and plumage spectrometry. We weighed individuals as nestlings and as nutritionally independent juveniles. We collected a retrix from each juvenile and used it to calculate the average feather growth bar length and mean brightness, both condition-dependent plumage traits.

Results/Conclusions

Although nestlings were heavier in the wildlands, juveniles were heavier in the suburbs, suggesting the suburban diet is limiting for nestlings, but not juveniles. However, wildland juveniles have larger growth bars and brighter plumage, indicating the quality of their diet during development is superior. Plumage coloration plays a role in status-signaling among juvenile scrub-jays. Suburban-born birds frequently migrate to the wildlands where they may be perceived as subordinate because of their duller plumage. These patterns may lead to a mismatch between body condition, plumage coloration and/or signal content. These changes in the content or honesty of plumage signals may impact metapopulation dynamics and the recolonization of restored habitat.