Paul A. Porneluzi

Landscape effects mediate breeding bird abundance in midwestern forests

We examine the influence of both local habitat and landscape variables on avian species abundance at forested study sites situated within fragmented and contiguous landscapes. The study was conducted over a six year period (1991–1996) at 10 study sites equally divided between the heavily forested Missouri Ozarks and forest fragments in central Missouri. We found greater species richness and diversity in the fragments, but there was a higher percentage of Neotropical migrants in the Ozarks. We found significant differences in the mean number of birds detected between the central Missouri fragments and the unfragmented Ozarks for 15 (63%) of 24 focal species. We used stepwise regression to determine which of 12 local vegetation variables and 4 landscape variables (forest cover, core area, edge density, and mean patch size) accounted for the greatest amount of variation in abundance for 24 bird species. Seven species (29%) were most sensitive to local vegetation variables, while 16 species (67%) responded most strongly to one of four landscape variables. Landscape variables are significant predictors of abundance for many bird species; resource managers should consider multiple measures of landscape sensitivity when making bird population management decisions.

Bird Response to Clear Cutting in Missouri Ozark Forests

Abstract We evaluated changes in breeding bird density and shifts in territory distribution with respect to clear cutting and timber stand improvement (TSI) of even-aged stands on >300 ha experimental management units as part of the Missouri Ozark Forest Ecosystem Project. After one harvest entry, clear cutting had positive effects on density of indigo bunting (Passerina cyanea), prairie warbler (Dendroica discolor), and yellow-breasted chat (Icteria virens) and negative effects on density of Acadian flycatcher (Empidonax virescens), ovenbird (Seiurus aurocapilla), and worm-eating warbler (Helmitheros vermivorus). In buffer regions within 100 m of clearcuts, indigo bunting, hooded warbler (Wilsonia citrina), wood thrush (Hylocichila mustelina), and Kentucky warbler (Oporornis formosus) densities increased and ovenbird density decreased. Breeding bird densities did not change in interior regions >100 m from clearcuts except for a small increase for wood thrush. Breeding Acadian flycatcher and ovenbird showed greater use of stands not treated with TSI. We recommend combining adjoining stands to keep clearcut sizes between 8 ha and 13 ha to reduce negative effects on ovenbirds by cutting. We suggest a 7-year offset between the timing of clear cutting and TSI to reduce their combined effects on ovenbird.

Breeding density affects point-count accuracy in Missouri forest birds

Abstract We compared 50-m fixed-radius point-count detections for four bird species with density data from spot-mapping in order to evaluate the relationship between monitoring methodologies. We conducted this study in five Missouri oak-hickory forest study sites over eight years. There were significant positive correlations between monitoring methods, but the strength of these relationships varied for Acadian Flycatchers (Empidonax virescens), Ovenbirds (Seiurus aurocapilla), Worm-eating Warblers (Helmitheros vermivorus), and Wood Thrushes (Hylocichla mustelina). There was significant bias associated with the point-count detections for Acadian Flycatchers, Worm-eating Warblers, and Wood Thrushes. The direction and degree of bias varied; for example, Acadian Flycatchers and Worm-eating Warblers were on average significantly overestimated by point counts, whereas the Wood Thrush was significantly underestimated and Ovenbirds were slightly underestimated. The magnitude and direction of the bias error varied with spot-map density estimates of the species, but was not related to specific study sites or years. Thus 50-m radius fixed-radius point counts appear to reflect general density trends for the four species, especially for Ovenbirds, but there are also density related biases associated with point-count detections.

Long-term dynamics of bird use of clearcuts in post-fledging period

ABSTRACT We focus on bird use of clearcuts resulting from even-aged management as part of the Missouri Ozark Forest Ecosystem Project (MOFEP). The long-term nature of MOFEP allows us to present a 15-year monitoring of bird use of MOFEP clearcuts in July using constant effort mist-netting. This provides insight into the dynamics of forest bird use of clearcuts during the post-fledging period for both early succession and mature forest breeding birds. We operated nets ∼10,080 hrs and captured 4,711 individuals, with 2,718 individuals considered mature forest breeding birds, and 1,993 individuals considered early succession species. There were few birds occupying clearcuts in year 1, immediately after cutting. Mean captures of all species as a group showed a significant curvilinear trend over time with an early peak in year 3 to 4 followed by decline. Mean captures of early succession species showed a significant trend of an early peak in year 3 followed by steady decline. Mature forest breeding species captures showed a significant curvilinear trend that increased gradually up to a peak around 6–9 years after harvest and then declined. Capture rates suggest that large numbers of birds use clearcuts in the decade after the clearcuts are formed. The abundance of forest-breeding birds in clearcuts in late summer equals or even exceeds the abundance of clearcut-breeding birds found there. This suggests that clearcuts may be an important habitat for mature forest breeding birds after they breed in mature habitats. More work on post-fledging behavior of migratory birds is needed to determine those species which require early succession habitats such as clearcuts and those species which simply take advantage of such habitats should they occur in the vicinity.