The Plight of Migrant Birds Wintering in the Caribbean: Rainfall Effects in the Annual Cycle

Here, we summarize results of migrant bird research in the Caribbean as part of a 75th Anniversary Symposium on research of the United States Department of Agriculture Forest Service, International Institute of Tropical Forestry (IITF). The fate of migratory birds has been a concern stimulating research over the past 40 years in response to population declines documented in long-term studies including those of the IITF and collaborators in Puerto Rico’s Guánica dry forest. Various studies indicate that in addition to forest loss or fragmentation, some migrant declines may be due to rainfall variation, the consequences of which may carry over from one stage of a migrant’s annual cycle to another. For example, the Guánica studies indicate that rainfall extremes on either the temperate breeding or tropical wintering grounds affect migrant abundance and survival differently depending on the species. In contrast, IITF’s collaborative studies of the migrant Kirtland’s Warbler (Setophaga kirtlandii) in the Bahamas found that late winter droughts affect its annual survival and breeding success in Michigan. We review these IITF migrant studies and relate them to other studies, which have improved our understanding of migrant ecology of relevance to conservation. Particularly important is the advent of the full annual cycle (FAC) approach. The FAC will facilitate future identification and mitigation of limiting factors contributing to migrant population declines, which for some species, may be exacerbated by global climate change

Status of the California Condor (\u3ci\u3eGymnogyps californianus\u3c/i\u3e) and Efforts to Achieve its Recovery

The California Condor (Gymnogyps californianus; hereafter “condor”; Fig. 1) has long been symbolic of avian conservation in the United States. Its large size, inquisitiveness, and association with remote places make it highly charismatic, and its decline to the brink of extinction aroused a continuing public interest in its plight. By 1982, only 22 individuals remained of this species whose range once encompassed much of North America. The last wild bird was trapped and brought into captivity in 1987, which rendered the species extinct in the wild (Snyder and Snyder 1989). In the 1980s, some questioned whether viable populations could ever again exist in the natural environment, and whether limited conservation funds should be expended on what they viewed as a hopeless cause (Pitelka 1981). Nevertheless, since that low point, a captive-breeding and release program has increased the total population by an order of magnitude, and condors fly free again in California, Arizona, Utah, and Baja California, Mexico (Fig. 2). At this writing (summer 2009), more than 350 condors exist, 180 of which are in the wild (J. Grantham pers. comm.). The free-living birds face severe challenges, however, and receive constant human assistance. The intensive management applied to the free-living populations, as well as the ongoing monitoring and captive-breeding programs, are tremendously expensive and become more so as the population grows. Thus, the program has reached a crossroads, caught between the financial and logistical pressures required to maintain an increasing number of condors in the wild and the environmental problems that preclude establishment of naturally sustainable, free-ranging populations. Recognizing this dilemma, in November 2006, Audubon California requested that the American Ornithologists’ Union (AOU) convene an independent panel to evaluate the California Condor Recovery Program. The National Audubon Society (NAS) and the AOU have a long history of interest and involvement in condor recovery. The NAS helped fund Carl Koford’s pioneering studies of condor biology in the 1940s (Koford 1953). A previous panel jointly appointed by the NAS and AOU examined the plight of the condor in the late 1970s, and their report (Ricklefs 1978) laid the groundwork for the current conservation program. The NAS was a full partner with the U.S. Fish and Wildlife Service (USFWS) in the early days of the program, from 1980 through 1988. Ricklefs (1978) recommended that the program “be reviewed periodically by an impartial panel of scientists,” and this was done annually by an AOU committee for several years after the release of the report, but the condor program has not been formally and thoroughly reviewed since the mid-1980s. Audubon California believed that the recovery program was operating with a recovery plan (USFWS 1996) widely acknowledged to be outdated, and that issues that were impeding progress toward recovery needed outside evaluation in order for the USFWS, which administers the program, and other policy makers to make the best decisions about the direction of the program (G. Chisholm pers. comm.). Such an evaluation would also help funding organizations better invest in the program

Effects of low impact selective logging on an understory bird community in the Tapajós National Forest, Pará, Brazil

This study compares the avian response to low impact selective logging by comparing bird species distribution in control and cut forest during five years, with before and post-harvest samples. Ordination analysis showed that the similarity of the bird community post-harvest was lesser than the similarity of samples before harvest. Moreover, the order of abundances of the 43 most common species changed between before and 3 to 4 years post-harvest in the logged forest. Logging affected capture rates for 20 species, either directly or with an interaction with time. The terrestrial insectivorous and mixed-species flocks were the guilds most affected by logging. Both guilds showed decline, correlated with time, in abundances in cut forest. Obligate army ant followers and arboreal insectivorous did not show differences between cut and control forest, but some species in these guilds showed logging effects, either directly or with an interaction between time and logging. Frugivores also did not show logging effects. Nectarivores increased in both the cut forest and in the control forest. Temporal effects of increase or decline occurred in guilds and in 12 species occurring in the cut and control forest. This result suggests that temporal changes in the cut forest may have resulted from succession and temporal changes in the control forest may have resulted from nearby harvest with 40m³/ha intensity in adjacent forest blocks.Este estudo compara a resposta de uma comunidade aves à exploração madeireira de baixo impacto através da distribuição das espécies em floresta controle e manejada ao longo de cinco anos com amostragem pré e pós-exploração. O procedimento de ordenação mostrou que a similaridade da comunidade de aves após a exploração madeireira foi menor que a similaridade entre as amostras do período de pré-exploração. Além disso, a ordem das abundâncias das 43 espécies mais comuns foi alterada entre o período anterior à exploração e 3 a 4 anos após a exploração na floresta manejada. A exploração afetou as taxas de captura de 20 espécies, diretamente ou através de uma interação com o tempo. Os insetívoros terrícolas e os insetívoros que seguem bandos mistos foram as guildas mais afetadas pela exploração madeireira. Ambas as guildas mostraram declínio, correlacionado com o tempo, em suas abundâncias em floresta manejada. Insetívoros seguidores de formigas e insetívoros arborícolas não apresentaram diferenças entre a floresta manejada e controle, apesar de algumas espécies dessas guildas terem apresentado efeitos relacionados ao manejo florestal, diretamente ou através de uma interação entre o tempo e o manejo. Frugívoros também não apresentaram efeitos significativos relacionados ao manejo florestal. Nectarívoros aumentaram tanto na floresta explorada como na floresta controle. Efeitos temporais de aumento ou declínio observados em guildas e em 12 espécies ocorreram tanto na floresta controle como na floresta explorada. Este resultado sugere que mudanças temporais na área explorada podem estar relacionadas à sucessão enquanto que mudanças temporais na floresta controle podem estar relacionados à exploração com intensidade de 40m³/ha de parcelas adjacentes

Appendix C. Life-stage simulation analysis.

Life-stage simulation analysis