Survival of grasshopper sparrows (Ammodramus savannarum) during two important life stages in grassland managed with fire and grazing

Hovick, Torre J.

doi:10.31274/etd-180810-470

Cited by 1 publication

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“…Nest success alone may lead to inflated estimates of overall survival (Knutson et al 2006). For example, in the pastures we studied, survival of Grasshopper Sparrow nests ranged from 13 to 23% (Hovick 2010). The addition of postfledging survival to nest-survival rates yields an overall probability of survival of 2% in graze-and-burn pastures and 7% in patch-burn grazed pastures.…”

Section: Discussionmentioning

confidence: 99%

Postfledging Survival of Grasshopper Sparrows in Grasslands Managed with Fire and Grazing

Hovick¹,

Miller²,

Koford³

et al. 2011

The Condor

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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.

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Section: Discussionmentioning

confidence: 99%