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Abstract Intensification of livestock production has reduced heterogeneity in vegetative structure in managed grasslands, which has been linked to widespread declines in grassland songbird populations throughout North America. Patch-burn grazing management aims to restore some of that heterogeneity in vegetative structure by burning discrete pasture sections, so that cattle preferentially graze in recently burned areas. Although patch-burn grazing can increase reproductive success of grassland songbirds, we know little about possible interactions with regional variation in predator communities or brood parasite abundance, or annual variation in weather conditions. Using six years of data from two tallgrass prairie sites in eastern Kansas, USA, we tested effects of patch-burn grazing on the rates of brood parasitism, clutch size, nest survival, and fledging success of three common grassland songbirds, Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Grasshopper Sparrows (Ammodramus savannarum), among pastures managed with patch-burn grazing versus pastures that were annually burned and either grazed or ungrazed. Dickcissel nests experienced lower parasitism (72.8 ± 4.6% SE vs. 89.1 ± 2.2%) and Eastern Meadowlarks had higher nest survival (63.2 ± 20.5% vs. 16.5 ± 3.5%) in annually burned and ungrazed pastures than pastures managed with patch-burn grazing. However, average number of host fledglings per nesting attempt did not differ among management treatments for any species. Annual variation in weather conditions had a large effect on vegetation structure, but not on reproductive success. Probability of brood parasitism was consistently high (25.5‒84.7%) and nest survival was consistently low (9.9–16.9%) for all species pooled across treatments, sites, and years, indicating that combined effects of predation, parasitism and drought can offset potential benefits of patch-burn grazing management previously found in tallgrass prairies. Although differences in reproductive success among management treatments were minimal, patch-burn grazing management could still benefit population dynamics of grassland songbirds in areas where nest predators and brood parasites are locally abundant by providing suitable nesting habitat for bird species that require greater amounts of vegetation cover and litter, generally not present in burned pastures.
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Interannual climate variation influences nest initiation date and nest productivity of the Red-cockaded Woodpecker at the northwestern edge of its range
Abstract Climate change, including directional shifts in weather averages and extremes and increased interannual weather variation, is influencing demography and distributions for many bird species. The Ouachita Mountains ecoregion in southeast Oklahoma and west-central Arkansas contains 2 populations of the Red-cockaded Woodpecker (Dryobates borealis, RCW), a federally endangered, cooperatively breeding species. Since this region is at the RCW’s northwestern range periphery, ecological thresholds likely are limiting for the species. Therefore, populations in this region may be more sensitive to climate change-associated weather variation and unpredictability. We used 26 years of nesting data (1991–2016) from the 2 RCW populations to determine if interannual weather variation has affected nesting phenology and productivity. For each population, we used daily temperature and precipitation data for 3 periods (30 and 60 days before nesting; 40 days overlapping the nesting period) to determine how weather influences median nesting date and average clutch size and numbers of fledglings. In a separate analysis, we used shorter time windows with individual nests as replicates to determine how discrete weather events (e.g., minimum and maximum temperatures and intense precipitation events) affect nest success and partial brood loss. For both Oklahoma and Arkansas populations, warmer early spring temperatures generally advanced nesting and increased clutch size and fledgling number. However, the effects of average precipitation varied depending on the amount and duration of precipitation in different time periods. At the nest level, most variables reflecting discrete temperature and precipitation events were unrelated to nest success and brood loss, suggesting that factors other than weather (e.g., habitat quality and predation) more strongly influenced the nesting output of individual RCW broods. Our results indicate RCWs are responding to interannual weather variation in complex and variable ways. However, warming trends may generally be having positive effects on the species at the northwestern edge of its range.
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- Award ID(s):
- 1946093
- PAR ID:
- 10318996
- Date Published:
- Journal Name:
- Ornithological Applications
- Volume:
- 123
- Issue:
- 2
- ISSN:
- 0010-5422
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/ornithapp/duab013
