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Keyword: reproduction

Demography of Northern goshawks in northern Arizona, 1991-1996

Publications Posted on: March 04, 2020
We studied 282 nesting attempts on 107 territories of Northern Goshawks (Accipiter gentilis) on the Kaibab Plateau in northern Arizona from 1991–1996. Mark-recapture methods were used to estimate recruitment, turnover of adults on territories, fi delity to territories by adults, and apparent annual survival of breeding adults. Territories were regularly spaced at a mean nearest-neighbor distance of 3.9 km.

Reproduction and dispersal of biological soil crust organisms

Publications Posted on: November 20, 2019
Biological soil crusts (BSCs) consist of a diverse and highly integrated community of organisms that effectively colonize and collectively stabilize soil surfaces. BSCs vary in terms of soil chemistry and texture as well as the environmental parameters that combine to support unique combinations of organisms - including cyanobacteria dominated, lichen-dominated, and bryophyte-dominated crusts.

Factors affecting lifetime reproduction, longterm territory-specific reproduction, and estimation of habitat quality in northern goshawks

Publications Posted on: May 29, 2019
One measure of habitat quality is a species’ demographic performance in a habitat and the gold standard metric of performance is reproduction. Such a measure, however, may be misleading if individual quality is a fitness determinant.

Associations between forest fire and Mexican spotted owls

Publications Posted on: August 01, 2018
In 1993, the US Fish and Wildlife Service listed the Mexican spotted owl (Strix occidentalis lucida) as threatened, in part because of the rising threat to its habitat from stand-replacing wildfires. In 1997, we surveyed 33 owl sites that, in the previous four years, had burned at various levels ranging from light controlled burns to stand-replacing fires.

Northern Goshawks: A 20 year study of ecology and habitat on the Kaibab Plateau

Pages Posted on: August 08, 2017
Research on the Kaibab has shown that goshawks, predators of birds and small mammals, are strongly food-limited. The local suite of prey depends on the amount, quality, and intermixture of the particular habitats needed by each prey. These include a fine-scale mix of small groups of mature trees with interlocking crowns for tree squirrels, woodpeckers, grouse, and other birds, and scattered, small grass-forb openings for rabbits, ground squirrels, grouse, and other prey. Interestingly, this habitat mix characterized the natural conditions of the ponderosa pine and mixed conifer forests on the Kaibab Plateau before initiation of fire suppression and organized tree harvests.

Long-term demography of the Northern Goshawk in a variable environment

Publications Posted on: May 17, 2017
The Nearctic northern goshawk (Accipiter gentilis atricapillis) is a resident of conifer, broadleaf, and mixed forests from the boreal to the southwestern montane regions of North America.

Northern goshawks on the Kaibab Plateau: A 20-year investigation into factors affecting their demography

Science Spotlights Posted on: August 26, 2016
The elusive northern goshawk, its forest habitats, and the habitats of its bird and mammal prey are significant conservation issues related to the management of forests throughout the hawk’s North American range.  The Rocky Mountain Research Station has been enumerating the population size and documenting the population ecology and demography of individual goshawks on Arizona’s Kaibab Plateau for 20 years with the objective of identifying the vegetation composition and structure of forests habitats that best supports their survival and reproduction.

Translocation as a conservation tool for Agassiz's desert tortoises: Survivorship, reproduction, and movements

Publications Posted on: July 29, 2013
We translocated 120 Agassiz's desert tortoises to 5 sites in Nevada and Utah to evaluate the effects of translocation on tortoise survivorship, reproduction, and habitat use. Translocation sites included several elevations, and extended to sites with vegetation assemblages not typically associated with desert tortoises in order to explore the possibility of moving animals to upper elevation areas.

Ungulate herbivory on Utah aspen: Assessment of longterm exclosures

Publications Posted on: May 02, 2013
The role of livestock grazing and big-game browsing in the decline of aspen (Populus tremuloides Michx.) in the Intermountain West has long been questioned.All known aspen exclosures (n=8) on the Dixie and Fishlake National Forests in south-central Utah were measured during late summer of 1995 and 1996 to determine aspen stem dynamics, successional status, and understory species composition.

A review of climate change effects on terrestrial rangeland birds

Publications Posted on: April 26, 2011
We evaluated existing literature on predicted and known climate change effects on terrestrial rangeland birds. We asked the following questions: 1) How does climate change affect birds? 2) How will birds respond to climate change? 3) Are species already responding? 4) How will habitats be impacted?