Avian Nest Success in Relation to Past Grazing Regimes in a Montane Riparian System

Abstract

One possible link between livestock grazing and bird population declines is variation in nest predation rates. To explore this possibility we documented vegetational differences in a montane riparian community subdivided by a fence, one side of which traditionally has been summer-grazed, and the other side rested from grazing for 30 years. We found that ground vegetation was more abundant, willows (Salk spp.) less abundant, and vertical vegetational diversity was lower on the grazed relative to the rested side. Predation rates on real nests were higher on the grazed side compared to the rested side. Artificial nests were placed (1) in mixed conifer vegetation to mimic the most common nest types currently present in the riparian zone, (2) in streamside willows that differed in abundance across the fence, and (3) in old-willow remnants distant from the stream, which were equally abundant on both sides of the fence. All artificial above-ground nests, and ground nests in the old-willow experiment, suffered greater predation rates on the grazed compared to the rested side. Thus, livestock grazing may not only affect availability of nesting substrates for riparian birds by reducing streamside vegetation, but could influence bird populations by facilitating nest predation, possibly by increasing detectability of nests or through changes in predator assemblage.

Change in status of green peafowl Pavo muticus (Family Phasianidae) in Southcentral Vietnam: A comparison over 15 years

“…The habitat model showed that presence of domestic cattle had a negative effect on the number of green peafowl, with large numbers of cattle resulting in few green peafowl. Overgrazing in the area causes habitat degradation, especially on ground vegetation and year round grazing may disturb ground nesting birds during breeding season (Ammon and Stacey, 1997). A study in China showed that grazing intensities had negative effects on grassland biomass especially above ground biomass and during drought periods, plants were more vulnerable to grazing (Liang Yan et al, 2013).…”

Teste do efeito de borda na predação de ninhos naturais e artificiais no Cerrado

“…Porém, em outros trabalhos, essa diferença ocorreu com menor (e.g. AMMON & STACEY 1997, WILSON et al 1998) ou com maior sucesso em ninhos artificiais quando comparados aos naturais (e.g. ROPER 1992ROPER , 2000ROPER , 2003.…”

The use of digital photos to assess visual cover for wildlife in rangelands

“…Grazing alters the structure of grasslands through the removal of plant biomass, thus potentially increasing the susceptibility of ground-nesting birds, as well as small grassland mammals, to predation. The resulting loss of suitable habitat and increased predation risk due to grazing may be a contributing factor to the decline in grassland bird populations in western rangelands (Ammon and Stacey, 1997;Brennan and Kuvlesky, 2005).…”