Dataset Information

Reproductive success of Eastern Bluebirds (Sialia sialis) varies with the timing and severity of drought.

ABSTRACT: Drought affects avian communities in complex ways. We used our own and citizen science-generated reproductive data acquired through The Cornell Lab of Ornithology's NestWatch Program, combined with drought and vegetation indices obtained from governmental agencies, to determine drought effects on Eastern Bluebird (Sialia sialis L.) reproduction across their North American breeding range for the years 2006-2013. Our results demonstrate that some aspects of bluebird reproductive success vary with the timing and severity of drought. Clutch size was unaffected by any level of drought at the time of clutch initiation or during the 30 to 60 days prior to clutch initiation. Hatching and fledging rates decreased as drought severity increased. Drought conditions occurring at least 30 days prior to the date eggs should have hatched and 60 days prior to the date offspring should have fledged negatively affected reproduction. We also demonstrate the value of datasets generated by citizen scientists in combination with climate data for examining biotic responses at large temporal and spatial scales.

SUBMITTER: Carleton RE

PROVIDER: S-EPMC6688811 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Reproductive success of Eastern Bluebirds (Sialia sialis) varies with the timing and severity of drought.

Carleton Reneé E RE Graham John H JH Lee Adel A Taylor Zachary P ZP Carleton Jon F JF

PloS one 20190809 8

Drought affects avian communities in complex ways. We used our own and citizen science-generated reproductive data acquired through The Cornell Lab of Ornithology's NestWatch Program, combined with drought and vegetation indices obtained from governmental agencies, to determine drought effects on Eastern Bluebird (Sialia sialis L.) reproduction across their North American breeding range for the years 2006-2013. Our results demonstrate that some aspects of bluebird reproductive success vary with ...[more]

PMID: 31398191

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Project description:We analyzed the reproductive success of eastern bluebirds (Sialia sialis) nesting in apple orchards and non-orchard nest-boxes in southern Ontario, Canada, from 1988 to 2018. Using data from 2397 nest-boxes monitored at 20 orchard sites and 52 non-orchard sites, we first modeled phenological parameters typically linked to climate change across both site types. We found that the first egg of each brood was laid significantly earlier in the season each year over our 31-year study. Clutch initiation occurred 4 days earlier in the spring in 2018 compared to 1988. Average clutch size in the first or second brood did not change significantly during our 31-year study; however, clutches were significantly smaller in orchards compared to non-orchards (0.10 ± 0.03 fewer eggs between sites). Nests built in orchards were also at 6.1-fold greater risk of parasitism and 2.1-fold greater risk of depredation than nests in non-orchards. After accounting for depredation and nest parasitism, hatching success was still significantly lower in orchards than in non-orchards. Overall, hatching success was 4%-5% lower in orchards. The probability of successfully fledging did not differ significantly between site types. In 2012, a ban on use of the organophosphate insecticide azinphos-methyl in orchards was enacted in Canada. We did not find a difference in hatching or fledging success in orchards after the ban. In our assessment of available data, we conclude that any pesticide effect on hatching success of eastern bluebirds in sprayed orchards is most likely the consequence of long-term exposure to dichlorodiphenyltrichloroethane (DDT) compounds in orchard soils and bioaccumulation in eggs rather than pesticides in use since regulation of DDT in the 1970s. Environ Toxicol Chem 2021;40:3369-3378. © 2021 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Project description:BackgroundA study on the Whiskered Tern Chlidonias hybrida was carried out between 2002 and 2009 in wetlands of eastern Spain to evaluate how water level fluctuation affects its reproductive success (hatching, fledgling and breeding success). This species is catalogued as Vulnerable in Spain and has an unfavorable conservation status in Europe.MethodsOur study includes 18 sampling areas from five wetlands, covering a total of 663 nests, 1,618 eggs, 777 nestlings and 225 fledglings. The colonies were visited at least twice per week in breeding period. The number of eggs and/or nestlings present in each nest were annotated each time the colonies were visited with the aim to compare the evolution of these parameters with time. Hatching success was calculated as the proportion of egg that hatched successfully. Fledgling success and breeding success were calculated as the proportion of chicks that fledged successfully and the proportion of eggs that produced fledglings. We used the Kruskal-Wallis test to analyze the differences in the dependent variables hatching, fledgling and breeding success among the wetlands and the sampling areas. We explored the relationship between the different reproductive success with the average fluctuation rate and the anchoring depth of nests, using statistics of the linear regression.ResultsIt was observed that the reproductive success varied significantly in the interaction among the different categories of water level fluctuation and the different areas (using the Kruskal-Wallis test). Our records showed that pronounced variations in water level destroyed several nests, which affected the Whiskered Tern reproductive success. Considering all events that occurred in 18 areas, the mean (±SD) of nests, eggs and nestlings that were lost after water level fluctuations were of 25.60 ± 21.79%, 32.06 ± 27.58% and 31.91 ± 21.28% respectively, also including the effects of rain and predation.DiscussionUnfavorable climatic events, such as strong wind, rain or hail, also caused the loss of nests, eggs and nestlings, even when wetland water levels remained constant. The influence of the anchorage depth of the nest and the water level fluctuation rate were analyzed and did not provide statistically significant results. It was not possible to establish a clear pattern on these latter variables, so further studies are needed to obtain more significant results. We propose to undertake similar studies in wetlands where the water level can be regulated, with the range of nest anchorage depth on the emergent vegetation being between 30 and 60 cm, which could improve the reproductive success in this kind of habitats. As recommendation, in water level controlled wetlands (that use sluices), it should not vary more than ±6 cm in a short time (1-2 days) once the nests are established since it negatively affects their reproductive success.

Dataset Information

Reproductive success of Eastern Bluebirds (Sialia sialis) varies with the timing and severity of drought.

Publications

Reproductive success of Eastern Bluebirds (Sialia sialis) varies with the timing and severity of drought.

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