The availability of winter food may strongly influence overwinter survival and, hence, limit certain bird populations in northern regions. Using the Jolly—Seber method of estimating survival rates from recapture and reobservation data, we compared the survival rates of 418 individually marked Black—capped Chickadees, Parus atricapillus, having access to supplemental food with those of 158 chickadees without access to supplemental food. During three winters (October through April, 1982—1985) chickadees with access to supplemental food had higher average monthly survival rates (95 vs. 87%), higher overwinter survival rates (69 vs. 37%), and higher standardized body masses (an additional 0.13 g) than birds on control sites. Differential survival occurred primarily during months with severe weather (> 5 d below —18°C). During these months, high energy demands probably made it difficult for birds without access to supplemental food to obtain sufficient energy from dispersed natural sources. In addition, during periods of extreme weather when foraging may be difficult, the extra fat carried by individuals that are supplementally fed may increase the probability of survival.
Worldwide shale-gas development has the potential to cause substantial landscape disturbance. The northeastern U.S., specifically the Allegheny Plateau in Pennsylvania, West Virginia, Ohio, and Kentucky, is experiencing rapid exploration. Using Pennsylvania as a proxy for regional development across the Plateau, we examine land cover change due to shale-gas exploration, with emphasis on forest fragmentation. Pennsylvania's shale-gas development is greatest on private land, and is dominated by pads with 1-2 wells; less than 10 % of pads have five wells or more. Approximately 45-62 % of pads occur on agricultural land and 38-54 % in forest land (many in core forest on private land). Development of permits granted as of June 3, 2011, would convert at least 644-1072 ha of agricultural land and 536-894 ha of forest land. Agricultural land conversion suggests that drilling is somewhat competing with food production. Accounting for existing pads and development of all permits would result in at least 649 km of new road, which, along with pipelines, would fragment forest cover. The Susquehanna River basin (feeding the Chesapeake Bay), is most developed, with 885 pads (26 % in core forest); permit data suggests the basin will experience continued heavy development. The intensity of core forest disturbance, where many headwater streams occur, suggests that such streams should become a focus of aquatic monitoring. Given the intense development on private lands, we believe a regional strategy is needed to help guide infrastructure development, so that habitat loss, farmland conversion, and the risk to waterways are better managed.
Artificial nests frequently are used to assess levels and patterns of nest predation, but how well these nests measure rates of predation or trends in predation rates at real nests is unclear. We compared predation rates between 58 active Wood Thrush (Hylocichla mustelina) nests paired with 58 artificial nests designed to resemble Wood Thrush nests. Paired nests were available to the same predator community both spatially and temporally. Rates of nest predation were significantly lower for active Wood Thrush nests (33%) than for artificial nests (64%). Rates of parasitism by Brown-headed Cowbirds (Molothrus ater) also differed between the two groups. Twenty-six percent of active nests and none of the artificial nests were parasitized by cowbirds. During 1993 and 1994, we conducted three artificial nest trials on six study sites per year. Rates of predation were highest in small woodlots and declined with increasing forest patch size consistent with the trend reported for active nests on the same sites. Within sites, rates of predation varied among trials with the amount of variation highest on sites with high predation rates. Our results suggest that although artificial nests should not be used to measure actual rates of nest predation or parasitism, they may be valuable for detecting trends in rates of predation. However, because there are many potential biases associated with the use of artificial nests that may make interpretation of trend data difficult, we recommend using artificial nests primarily in pilot studies or in conjunction with active nests.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.