Carol I. Bocetti

Carry-Over Effects of Winter Climate on Spring Arrival Date and Reproductive Success in an Endangered Migratory Bird, Kirtland's Warbler (Setophaga kirtlandii)

ABSTRACT. Understanding how animals will adapt to climate change requires understanding how climate variables influence their biology year round, and how events in different seasons interact. Migratory birds may be especially vulnerable because of the wide range of geographic areas that they depend on throughout the annual cycle. We examined the potential effects of non-breeding season climate change on the breeding biology of Kirtlands Warbler (Setophaga kirtlandii, formerly Dendroica kirtlandii), an endangered songbird that breeds in the Northern Lower Peninsula of Michigan and winters in the Bahamas. Our objectives were to determine whether spring arrival dates on the breeding grounds correlate with late winter rainfall in non-breeding areas and whether this has consequences for reproductive success. We used data on spring arrival dates and number of fledglings per year, sampling many individuals across multiple years, to show that males arrive on breeding grounds later following drier winters. There was a strong male age * rainfall interaction, which indicates that first-time breeders were much more sensitive to changes in rainfall than experienced adults. Regardless of age, however, drier winters and delayed arrival and nest initiation were significantly associated with fewer offspring fledged. These results are important because the Caribbean region is currently experiencing a significant drying trend, and climate change models predict that the severity of this drought will continue to increase. Any resulting adjustments to the timing of migration could constrain spring arrival dates and limit reproductive success for the endangered Kirtlands Warbler, as well as other Neotropical migrants wintering in the Caribbean. RESUMEN. Comprender cómo los animales se adaptan al cambio climático requiere entender cómo las variables climáticas afectan su biología a lo largo del año, y cómo interactúan los eventos sucedidos en diferentes temporadas. Las aves migratorias pueden ser especialmente vulnerables dado el amplio espectro de áreas geográficas de las que ellas dependen a lo largo del ciclo anual. Examinamos los efectos potenciales del cambio climático en las temporadas no reproductivas sobre la biología reproductiva de Setophaga kirtlandii (antes Dendroica kirtlandii), un ave canora amenazadaque se reproduce en el norte de la peninsula inferior de Michigan y pasa el invierno en las Bahamas. Nuestros objetivos fueron determinar si las fechas de llegada a las áreas de reproducción en primavera se correlacionan con la precipitación del final del invierno en la áreas no reproductivas, y si lo anterior tiene consecuencias sobre el éxito reproductivo. Usamos datos de las fechas de llegada en primavera y el número de volantones por año, muestreando múltiples individuos a lo largo de múltiples años, y logramos demostrar que los machos llegan a las áreas de reproducción más tarde luego de inviernos más secos. Hubo una interaccián fuerte entre la edad de los machos y la precipitacián, de modo que los que se reproducían por primera vez fueron mucho más sensibles a los cambios en la precipitación que los adultos más experimentados. Sin embargo, independientemente de la edad, los inviernos más secos y la llegada e iniciación tardía de la anidación estuvieron significativamente asociados con un menor número de crías emplumadas. Estos resultados son importantes porque la región Caribe actualmente está experimentando una tendencia hacia la aridez y los modelos de cambio climático predicen que la severidad de la sequía continuará incrementándose. Cualquier desajuste en la sincronización de la migración que se produzca como consecuencia de lo anterior podría restringir las fechas de arribo en la primavera y limitar el éxito reproductivo de S. kirtlandii, así como de otros migrantes neotropicales que pasan el invierno en el Caribe.

Population increase in Kirtland's warbler and summer range expansion to Wisconsin and Michigan's Upper Peninsula, USA

The threatened Kirtlands warbler Dendroica kirtlandii breeds in stands of young jack pine Pinus banksiana growing on well-drained soils in Michigan, USA. We summarize information documenting the range expansion of Kirtlands warbler due to increased habitat management in the core breeding range in the Lower Peninsula of Michigan during 1990-2000. We collected records and conducted searches for the species in Michigans Upper Peninsula and Wisconsin over 1978-2000. During that time 25 males were found in Wisconsin and 90 males in the Upper Peninsula. We documented colonization of Michigans Upper Peninsula by six ringed males from the Lower Peninsula of Michigan. Four ringed birds also moved back to the core breeding range, including two males that made two-way movements between the core breeding range and the Upper Peninsula. Thirty-seven females were observed with males from 1995 to 2000, all in Michigan. Nesting activities were noted for 25 pairs and at least nine nests fledged young. One male ringed as a fledgling returned to breed in two subsequent years. After a 19-year period of population stability, the Kirtlands warbler population increased four-fold during 1990-2000, most likely in response to a tripling in habitat area. This increase in sightings and documented breeding may be related to habitat availability in Michigans Upper Peninsula and to saturation of habitat in the main breeding range. The increase in extra-limital records during 1995-1999 corresponds to the time when the population went frorn the minimum to the maximum projected population densities, and a decline in natural wildfire habitat was just offset by new managed habitat for the Kirtlands warbler.

Evaluation of Mist-net Sampling as an Index to Productivity in Kirtland's Warblers

Many applied and theoretical investigations require information on how productivity varies in time and space (Temple and Wiens 1989, DeSante 1995). Examples include studies of habitat quality, population trends, life-history tactics, and metapopulation dynamics. From a demographic perspective, reproductivity is the number of young, counted at a given time of year, produced per adult (e.g. Caswell 1989). Various measures have been used to estimate productivity. One of the most attractive is mist neting during the summer after young have left the nest, but ideally before they have left the studv area. Several programs use this approach, including the Constant Effort Sites Scheme of the British Trust for Ornithology (Baillie et al. 1986 Bibby et al. 1992) and the Monitoring Avian Productivity and Survivorship {MAPS) program (DeSante et al. 1993) in North America.

Impacts of Phragmites Management on Marsh Wren Nesting Behavior

Abstract We monitored territory density, nest density, date of nest initiation, nest height, and associated vegetation characteristics of Marsh Wrens (Cistothorus palustris) in two marshes managed with herbicide in late summer 2009 to control Phragmites. Average territory density declined fourfold from 2.39 to 0.54 territories/ha (one-tailed t-test, P  =  0.004), and average active nest density declined tenfold from 1.43 to 0.12 nests/ha (one-tailed t-test, P  =  0.055) between 2009 and 2010. The mean date of nest initiation was twice as late in 2010 (21 Jul) as in 2009 (15 Jun), one-tailed t-test, P  =  0.009. Mean nest height was similar (one-tailed t-test, P  =  0.20) in 2009 (86.4 cm) and 2010 (79.6 cm), but the vegetation took longer to reach these heights in 2010, particularly at Old Woman Creek National Estuarine Research Reserve. These results suggest large scale aerial herbicide applications to manage Phragmites compromised productivity of Marsh Wrens in the coastal marshes studied. Caution should be used when considering broadcast, aerial applications of herbicides to treat Phragmites in habitats of marsh-dependent, declining, avian species.

Cruise ships as a source of avian mortality during fall migration

Abstract Avian mortality during fall migration has been studied at many anthropogenic structures, most of which share the common feature of bright lighting. An additional, unstudied source of avian mortality during fall migration is recreational cruise ships that are brightly lit throughout the night. I documented a single mortality event of eight Common Yellowthroats (Geothlypis trichas) on one ship during part of one night in fall 2003, but suggest this is a more wide-spread phenomenon. The advertised number of ship-nights for 50 cruise ships in the Caribbean Sea during fall migration in 2003 was 2,981. This may pose a significant, additional, anthropogenic source of mortality that warrants further investigation, particularly because impacts could be minimized if this source of avian mortality is recognized.

Using a full annual cycle model to evaluate long-term population viability of the conservation-reliant Kirtland's warbler after successful recovery

Long-term management planning for conservation-reliant migratory songbirds is particularly challenging because habitat quality in different stages and geographic locations of the annual cycle can have direct and carry-over effects that influence the population dynamics. The Neotropical migratory songbird Kirtlands warbler Setophaga kirtlandii (Baird 1852) is listed as endangered under the U.S. Endangered Species Act and Near Threatened under the IUCN Red List. This conservation-reliant species is being considered for U.S. federal delisting because the species has surpassed the designated 1000 breeding pairs recovery threshold since 2001. To help inform the delisting decision and long-term management efforts, we developed a population simulation model for the Kirtlands warbler that incorporated both breeding and wintering grounds habitat dynamics, and projected population viability based on current environmental conditions and potential future management scenarios. Future management scenarios included the continuation of current management conditions, reduced productivity and carrying capacity due to the changes in habitat suitability from the creation of experimental jack pine Pinus banksiana (Lamb.) plantations, and reduced productivity from alteration of the brown-headed cowbird Molothrus ater (Boddaert 1783) removal programme. Linking wintering grounds precipitation to productivity improved the accuracy of the model for replicating past observed population dynamics. Our future simulations indicate that the Kirtlands warbler population is stable under two potential future management scenarios: (i) continuation of current management practices and (ii) spatially restricting cowbird removal to the core breeding area, assuming that cowbirds reduce productivity in the remaining patches by =41%. The additional future management scenarios we assessed resulted in population declines. Synthesis and applications. Our study indicates that the Kirtland’s warbler population is stable under current management conditions and that the jack pine plantation and cowbird removal programmes continue to be necessary for the long-term persistence of the species. This study represents one of the first attempts to incorporate full annual cycle dynamics into a population viability analysis for a migratory bird, and our results indicate that incorporating wintering grounds dynamics improved the model performance.

Re-evaluating the Bay-breasted Warbler breeding range: Nine years of presence in Lower Michigan

Abstract The breeding range of the Bay-breasted Warbler (Dendroica castanea) is thought to include only the northernmost portions of six northeastern and northcentral states in the United States. During a 10-year banding study of Kirtlands Warblers (Dendroica kirtlandii) in northern Lower Michigan, we caught 44 Bay-breasted Warblers outside of their reported migration dates during 9 of the 10 years. Two birds captured in 1997 were in breeding condition; one possessed a cloacal protuberance and the other a full brood patch. We also captured two hatching year birds with fleshy rictal flanges in 1997. We suggest that these records indicate a long term presence of Bay-breasted Warblers on breeding grounds considerably farther south than previously recorded.