No abstract

Animals inhabiting urban areas must simultaneously cope with the unique challenges presented by this novel habitat type while exploiting the distinctive opportunities it offers. The costs and benefits of urban living are often assumed to be consistent across time, but may in fact vary depending on the habitat features influencing them. Here we examine the glucocorticoid levels and body condition of song sparrows (Melospiza melodia) resident at urban and rural sites over four consecutive years to determine whether these traits, which may be linked to the relative costs and benefits of these respective habitats, are consistent over time. Glucocorticoid levels and body condition varied by year in both habitat types. While habitat alone did not influence glucocorticoid levels, there was a significant interaction between year and habitat, indicating that glucocorticoids differ between habitats in some years but not others. There was no discernable effect of habitat alone on body condition. Overall, these data suggest that the costs and benefits of inhabiting urban versus rural habitats differ substantially from year to year.

No abstract

Documenting the evolving processes associated with habitat restoration and how long it takes to detect avian demographic responses is crucial to evaluate the success of restoration initiatives and to identify ways to improve their effectiveness. The importance of this endeavor prompted the U.S. Fish and Wildlife Service and the USDA Natural Resources Conservation Service to evaluate their sun-to-shade coffee restoration program in Puerto Rico initiated in 2003. We quantified the responses of 12 resident avian species using estimates of local occupancy and extinction probabilities based on surveys conducted in 2015-2017 at 65 restored farms grouped according to time-since-initial-restoration (TSIR): new (2011-2014), intermediate (2007-2010), and old ( [2003][2004][2005][2006]. We also surveyed 40 forest sites, which served as reference sites. Vegetation complexity increased with TSIR, ranging between 35 and 40% forest cover in farms 6-9 years TSIR. Forest specialists (e.g. Loxigilla portoricencis) exhibited highest average occupancy in farms initially classified as intermediate (6-9 years) and old (>10 years), paralleling occupancy in secondary forests. Occupancy of open-habitat specialists (e.g. Tiaris olivaceus) was more variable, but higher in recently restored farms. Restoring the shade layer has the potential to heighten ecological services derived from forest specialists (e.g. frugivores) without losing the services of many open-habitat specialists (e.g. insectivores). Annual local extinction probability for forest specialists decreased with increasing habitat complexity, strengthening the potential value of shade restoration as a tool to enhance habitat for avifauna that evolved in forested landscapes.