Projecting demographic responses to climate change: adult and juvenile survival respond differently to direct and indirect effects of weather in a passerine population

Abstract

Few studies have quantitatively projected changes in demography in response to climate change, yet doing so can provide important insights into the processes that may lead to population declines and changes in species distributions. Using a long-term mark-recapture data set, we examined the influence of multiple direct and indirect effects of weather on adult and juvenile survival for a population of Song Sparrows (Melospiza melodia) in California. We found evidence for a positive, direct effect of winter temperature on adult survival, and a positive, indirect effect of prior rainy season precipitation on juvenile survival, which was consistent with an effect of precipitation on food availability during the breeding season. We used these relationships, and climate projections of significantly warmer and slightly drier winter weather by the year 2100, to project a significant increase in mean adult survival (12-17%) and a slight decrease in mean juvenile survival (4-6%) under the B1 and A2 climate change scenarios. Together with results from previous studies on seasonal fecundity and postfledging survival in this population, we integrated these results in a population model and projected increases in the population growth rate under both climate change scenarios. Our results underscore the importance of considering multiple, direct, and indirect effects of weather throughout the annual cycle, as well as differences in the responses of each life stage to climate change. Projecting demographic responses to climate change can identify not only how populations will be affected by climate change but also indicate the demographic process(es) and specific mechanisms that may be responsible. This information can, in turn, inform climate change adaptation plans, help prioritize future research, and identify where limited conservation resources will be most effectively and efficiently spent.

Habitat suitability through time: using time series and habitat models to understand changes in bird density

“…Although successional changes in plant structure and composition are due to the lack of human disturbance and suppression of natural disturbances (e.g., fire) since the early 1960s, our results support the conclusions of other studies that the indirect impact of climate change on bird abundance through changes in plant communities that provide bird habitat will be an important predictor of future climate-change impacts (Seoane et al 2004 and Inouye 2012). While rainfall did not explain a large percentage of the variance in densities, our results support previous work that show that annual weather rainfall patterns can contribute to vital rates (Chase et al 2005, Dybala et al 2013 and ultimately density (Silkey et al 1999, Dennis andOtten 2000).…”

Drought leads to reproductive quiescence in smooth‐billed anis: Phenotypic evidence for opportunistic breeding and reproductive readiness

“…The findings of this study (1) showed that the reproductive morphology of the smooth‐billed ani was similar to that observed in other birds such as domestic quail, fowl, emu, ostrich, goose, parakeet and drake (Aire, 2002; Aire & Soley, 2000; Leska, Kiezun, Kaminska, & Dusza, 2015; Parizzi et al, 2008; Peixoto et al, ; Reed, Cope, & Blackford, 2011); (2) indicated intense gonadal activity throughout the wet season that was consistently similar to what is described in other birds during the breeding season (Baraldi‐Artoni et al, ; Kim & Yang, ; Leska & Dusza, ; Peixoto et al, ; Tae et al, ); (3) and revealed remarkable signs of gonadal involution and low gametogenic activity after precipitation decreased. Birds inhabiting areas with adverse climate characteristics exhibit flexibility with regard to the timing and intensification of breeding activity whenever environmental conditions are satisfactory to ensure reproductive success and offspring survival (Cruz‐McDonnell & Wolf, ; Dybala, Eadie, Gardali, Seavy, & Herzog, ; Quintero, González‐Caro, Zalamea, & Cadena, ; Sandoval, ; Selwood et al, ). Increased precipitation rates usually determine high food and water availability in drought areas (Langin et al, ); therefore, opportunistic breeding usually follows intense single‐event rainfall and lasts until precipitation rates decline dramatically (Hahn et al, ; Mares, Doutrelant, Paquet, Spottiswoode, & Covas, ).…”

Linking phenological events in migratory passerines with a changing climate: 50 years in the Laurel Highlands of Pennsylvania

“…If mismatches with timing of peak resource abundance increase with warming, it may be less effective to raise a second brood [81]. Other fitness components, such as nest success of individual pairs and adult survival (e.g., [82]) may be impacted by phenological shifts. Consequently, we hesitate to say that shifts in timing will not have fitness impacts in the species we studied.…”