BigCB Catalog Detail: "Niche organizations in the Blue-Grey gnatcatcher"
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DatasetID 284
Name Niche organizations in the Blue-Grey gnatcatcher
Description The manner in which the niche exploitation patterns of gnat-catchers and other insectivorous birds are adapted to changes in the food supply was studied in California and Arizona. Standardized field techniques were developed to quantify changes in the birds' foraging beat, feeding tactics, food supply, and diet. Abundance of food and nest sites as well as structural characteristics of the vegetation are "releasers" for habitat selection. Territory boundaries are shifted to follow seasonal changes in the dispersion of food among the various habitats. The birds select the larger and more vulnerable prey at their preferred foraging stations, and change their foraging beat and diet in response to seasonal changes in prey availability. The energy requirements of dependent young are met by: devoting a greater proportion of time to foraging, increasing the foraging intensity, increasing the diversity of the foraging tactics and foraging beat, and capturing larger prey. These activities require that adults forage outside the normal "adaptive mode," which probably increases the expenditure of maintenance energy. It appears that food is an especially critical factor during the brief period when the brood is dependent on the adults. A new unit, the ecological "guild," is proposed for groups of species that exploit the same class of resources in a similar manner. The utility of the guild concept is discussed. It appears that niche segregation within the guild of foliage-gleaning insectivores is maintained by differences in the efficiency (reinforced by morphological differences) with which portions of a common range of situations can be exploited. The exploitation pattern is expressed opportunistically within limits largely set by morphology. The limiting specializations are related to structural features of the habitat and to behavioral and size characteristics of the prey, factors that tend to change less in space and time than do other features of the environment.

The principal study area was located on the Hastings Natural History Reservation, situated at the northern end of the Santa Lucia Mountains, in Monterey County, California.A total of 1197 hours were spent observing gnatcatchers on their breeding territories at the Hastings Reservation during the following periods: June 14-August 23, 1959; June 8-July 17, 1960; and March 4-August 8, 1963. Additional observation periods, totalling 25 days in the field, were spent during the early spring and late summer. Studies on the winter behavior of caerulea and melanura were carried out on three field trips to the Southwestern deserts in the winters of 1962 and 1963

TABLE 13. Arthropods in the diets of foliage-gleaning birds. The data are expressed as the percent of total prey individuals (n) that could be identified.

Section included on the Species Membership at Hastings, focusing on the Foliage Gleaning Guild
Physical Location
Publisher/Owner R. B. Root, Cornell University Department of Ecology and Evolutionary Biology, rbr1@cornell.edu, (607) 254-4237
Publication Date
Permissions Undetermined
Source Mark Stromberg NRS file
Contact Mark Stromberg
Type Biological Survey - Observational
Subject Animal
Geo. Extent Hastings Reserve
URL https://berkeley.app.box.com/files/0/f/372728021/1/f_42569603829
NRS Registry? yes
Format Paper
Timespan Start 1959
Timespan End 1963
Total Items
Databased Items 0   (as of 2012-08-31)
Comments Root, R. B. (1967). "Niche exploitation pattern of the Blue-Gray Gnatcatcher." Ecological Monographs 37: 317-350.

https://berkeley.app.box.com/files/0/f/372728021/1/f_42569603829

stable url: http://www.jstor.org/stable/pdf/1942327.pdf?acceptTC=true
Entered By Jessica Rothery
Last Updated 2015-12-28 12:35:08

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