Life history traits, such as clutch size, egg size, renesting rates, developmental rates, adult survival, and parental care behaviors (incubation, brooding, feeding young), vary extensively in geographic space. This project focuses on understanding why life history strategies vary among species and among geographic regions. We measure these traits and behaviors for the first time for relatively large numbers of species across a series of geographic sites: Arizona (ongoing work since 1985), Argentina (ended 2000), South Africa (ended 2004), New Zealand and Tasmania (ended), Venezuela (ended in 2008), and Borneo (new start in 2009).
A long-term (since 1985) study of a high elevation riparian ecosystem and bird community demonstrates climate effects on trophic interactions among plants, birds, mammals and nest predation. Key deciduous plants and several bird species have declined strongly in abundance, with one previously common bird species (MacGillivray'sWarbler) even going locally extinct. Large herbivores interact with climate change to cause plant losses (see next project).
Long-term declines in plants, and many bird species that rely on these plants, may reflect over-browsing by large herbivores, together with climate change (see above project). Herbivory and climate may interact to affect plant recruitment. The plants in turn affect abundances and types of species of birds and small mammals on the sites. Large-scale (9 ha) exclosures were erected on three sites in 2004 to examine the separate effects of herbivores versus climate on plants, birds, and small mammals.