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1 October 2016 Avian Nest Success along a Habitat Gradient in the Cross Timbers Oak Savanna
Nathan S. Holoubek, William E. Jensen
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Oak savanna, once widespread across central North America, has functionally vanished from most of its range due to land conversion or fire suppression and subsequent afforestation. Savanna-associated bird species have exhibited population declines as a result. One of the few areas containing remnant oak savanna is the vast Cross Timbers ecoregion of the south-central Unites States. Previous research in the Midwest showed some bird species exhibited higher rates of nest success (i.e., lower predation of eggs and nestlings) in restored savannas than in closed-canopy forests. Our objective was to quantify patterns of avian nest success across a gradient from open-canopy oak savanna to closed-canopy forest in the Cross Timbers ecoregion of southeastern Kansas. Daily nest survival rates for four common bird species—mourning dove (Zenaida macroura), yellow-billed cuckoo (Coccyzus americanus), brown thrasher (Toxostoma rufum), and northern mockingbird (Mimus polyglottos)—were modeled against covariates of woodland structure along the habitat gradient. Tree density and canopy cover had no significant effects on daily nest survival rate, but daily survival rates of brown thrasher and northern mockingbird nests showed positive trends with increasing shrub density. We expect restoration of oak savanna habitat would have little effect on nest survival of some common bird species in the naturally heterogeneous Cross Timbers ecoregion.

Nathan S. Holoubek and William E. Jensen "Avian Nest Success along a Habitat Gradient in the Cross Timbers Oak Savanna," The American Midland Naturalist 176(2), 234-246, (1 October 2016).
Received: 8 January 2016; Accepted: 15 June 2016; Published: 1 October 2016

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