Postfledging survival of Grasshopper Sparrows in grasslands managed with fire and grazing

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More accurate estimates of survival after nestlings fledge are needed for population models to be parameterized and population dynamics to be understood during this vulnerable life stage. The period after fledging is the time when chicks learn to fly, forage, and hide from predators. We monitored postfledging survival, causespecific mortality, and movements of Grasshopper Sparrows (Ammodramus savannarum) in grassland managed with fire and grazing. In 2009, we attached radio transmitters to 50 nestlings from 50 different broods and modeled their survival in response to climatic, biological, and ecological variables. There was no effect of treatment on survival. The factor most influencing postfledging survival was age; no other variable was significant. The majority of chicks (74%) died within 3 days of radio-transmitter attachment. We attributed most mortality to mesopredators (48%) and exposure (28%). Fledglings' movements increased rapidly for the first 4 days after they left the nest and were relatively stable for the remaining 10 days we tracked them. On average, fledglings took flight for the first time 4 days after fledging and flew ≥10 m 9 days after fledging. Our data show that the Grasshopper Sparrow's survival rates may be less than most models relying on nest-success estimates predict, and we emphasize the importance of incorporating estimates of survival during the postfledging period in demographic models.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Postfledging survival of Grasshopper Sparrows in grasslands managed with fire and grazing
Series title Condor
DOI 10.1525/cond.2011.100135
Volume 113
Issue 2
Year Published 2011
Language English
Publisher American Ornithological Society
Contributing office(s) Coop Res Unit Leetown
Description 9 p.
First page 429
Last page 437
Country United States
State Iowa
County Ringgold County
Online Only (Y/N) N
Additional Online Files (Y/N) N
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