Brood Provisioning and Nest Survival of Ardea herodias (Great Blue Heron) in Maine
2015
Auclair, Margaret M Meserve | Ono, Kathryn A. | Perlut, Noah G.
From 1983–2009, the number of coastal breeding pairs of Ardea herodias (Great Blue Heron [GBHE]) in Maine declined by 64%, and the number of occupied islands on which these birds bred declined by 40%. The Maine Department of Inland Fisheries and Wildlife listed the GBHE as a species of special concern in 2007, and expanded its annual monitoring to include inland colonies in 2009. To assess regional demographic differences, we compared the relationship between brood provisioning and nest survival of GBHEs in 1 coastal and 1 inland colony. In terms of brood-provisioning within the 2 colonies, the inland colony had significantly greater rates for the first 2 weeks post-hatch, but the coastal colony had greater rates in subsequent weeks. These differences did not affect either nest fate (≥1 chick fledged) or daily nest survival at the inland or coastal colony. In both colonies, the maximum number of nestlings observed at a nest was positively correlated with the number that subsequently fledged. Daily nest survival was positively associated with an increasing number of nestlings, earlier hatch dates, and increased brood-provisioning rates for 1–2-week-old chicks. Our results suggest that the number of nestlings per nest can be used as a proxy for nest survival in GBHE colonies in the northeastern part of their range. Furthermore, because nest survival was influenced by brood-provisioning rates during the first 1–2 weeks post-hatch, our results suggest that the most sensitive time for disturbance of GBHEs in the northeastern part of their range may be earlier in the nesting stage than previously thought.
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