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Reproductive failure and adult mortality drive viability of an endangered songbird population, not brood parasitism
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AI
DOI：10.5751/ACE-03053-210118.png)
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Abstract
En 中文
The Southern Mountain population of the Western Yellow-breasted Chat (Icteria virens auricollis) was designated as endangered in the south Okanagan Valley in Canada following extensive destruction of riparian breeding habitat over the previous century. Habitat restoration efforts began in 2001 and monitoring efforts were undertaken concurrently to identify threats to the persistence of the small remnant population. Putative threats included habitat degradation leading to low breeding female abundance and high rates of brood parasitism. Using 20 years of demographic data, we retrospectively quantified the influence of parasitism and density dependence on fertility and immigration. We then conducted a population viability analysis and projected extinction and quasi-extinction probabilities (falling below 20 breeding pairs), and probabilities of reaching the study region's carrying capacity 25 years into the future under six scenarios. Specifically, we tested changing rates of brood parasitism and of reproductive failure as could result from natural habitat succession, livestock grazing, urban development, or agricultural expansion. We simulated changes to adult survival rates, as might occur with climate change and extreme weather along migration routes. Simulated changes to parasitism rates did not produce significant changes in the risk of extinction or quasi-extinction, although parasitism significantly reduced fertility rates among individual nests. Simulating 20% and 40% increases to reproductive failure rates to reflect pressures from habitat degradation suppressed population growth rates and delayed or prevented the population from reaching the regional carrying capacity. There was an 8.9% chance of quasi-extinction by 2046 when adult survival rates were depressed by 20%. Overall, future management efforts would be more effectively allocated to riparian habitat restoration and protection to suppress reproductive failure rates, while mitigating direct anthropogenic threats to adults may also yield benefits for this Southern Mountain Chat population.
Keywords:
Bayesian population viability analysis
broodparasitism
Brown-headed Cowbird
endangeredspecies
immigration
integrated population model
Yellow-breasted Chat
Journal
A
IF:
1.1
Papers:
26
Citations:
839
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