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Evaluating the long-term management of introduced ungulates to protect the palila, an endangered bird, and its criticial habitat in subalpine forest of Mauna Kea, Hawai'i
Under the multiple-use paradigm, conflicts may arise when protection of an endangered species must compete with other management objectives. To resolve such a conflict in the Critical Habitat of the endangered Hawaiian honeycreeper, palila (Loxioides bailleui), federal courts ordered the eradication of introduced ungulates responsible for damaging the māmane (Sophora chrysophylla) forest on which palila depend. During 1980–2011, a total of 18,130 sheep (Ovis aries and O. gmelini musimon) and 310 goats (Capra hircus) were removed from Palila Critical Habitat (PCH) primarily by public hunters (54%) and secondarily by aerial shooting. Nevertheless, our analysis indicates that ungulates have increased over time. Palila numbers have declined sharply since 2003 due to long-term habitat degradation by ungulates and drought. Although culling ungulate populations has allowed some habitat improvement, their complete removal is necessary for palila to recover, especially given the potential for continued drought. Introduced predators are being controlled to reduce palila mortality, māmane and other native trees are being planted to restore some areas, and fencing is being constructed to prevent ungulate immigration. Funds are recently available for more effective eradication efforts, which are urgently needed to eliminate browsing damage in PCH and protect the palila from extinction.
Grassland birds orient nests relative to nearby vegetation
We studied orientation of nest sites relative to nearby vegetation for dabbling ducks (Cinnamon Teal, Anas cyanoptera ; Blue-winged Teal, A. discors ; Gadwall, A. strepera ; Mallard, A. platyrhynchos ; and Northern Shoveler, A. clypeata ) and Short-eared Owls ( Asio flammeus ) in ungrazed grassland habitat during 1995–1997 in westcentral Montana. We estimated an index of vegetation height and density in intercardinal directions (NE, SE, SW, NW) immediately around nests. All species oriented nests with the least vegetation to the southeast and the most vegetation to either the southwest or northwest. Furthermore, maximum vegetation around nests shifted from the southwest to the northwest with increasing nest initiation date, apparently as a response of individuals tracking seasonal change in the afternoon solar path. Thus, nests were relatively exposed to solar insolation during cool morning hours but were shaded from intense insolation in the afternoon throughout the breeding season. We suggest that nest microhabitat was selected in part to moderate the thermal environment.
Seasonal fecundity and source-sink status of shrub-nesting birds in a southwestern riparian corridor
Saltcedar ( Tamarix spp.) has increasingly dominated riparian floodplains relative to native forests in the southwestern U.S., but little is known about its impacts on avian productivity or population status. We monitored 86 Arizona Bell's Vireo ( Vireo bellii arizonae ), 147 Abert's Towhee ( Melozone aberti ), and 154 Yellow-breasted Chat ( Icteria virens ) nests to assess reproductive parameters in cottonwood-willow ( Populus-Salix ), saltcedar, and mesquite ( Prosopis spp.) stands along the San Pedro River, Arizona during 1999–2001. We also assessed source-sink status for each species in each vegetation type using field data combined with data from the literature. There were no significant differences in reproductive parameters between vegetation types for Abert's Towhee or Yellow-breasted Chat, although seasonal fecundity was quite low across vegetation types for the latter (0.75 ± 0.14; mean ± SE). Bell's Vireo had extremely low seasonal fecundity in saltcedar (0.10 ± 0.09) and significantly fewer fledglings per nest in saltcedar (0.09 ± 0.09) compared with cottonwood (1.07 ± 0.32). Point estimates of λ were substantially <1 for all three focal species in all habitats indicating the entire study area may be performing as a sink; 90% CI of included 1 only for Abert's Towhee across vegetation types and Bell's Vireo in cottonwood vegetation. These results are surprising given the San Pedro is considered to be one of the best remaining occurrences of lowland native riparian vegetation in the southwestern United States.
Book review: Feeding wild birds In America – Culture, commerce, and conservation
No abstract available.
Additional records of aspergillosis among passerine birds in Maryland and the Washington, DC metropolitan area
Two cases of aspergillosis involving four adult cowbirds ( Molothrus ater ) collected during the nesting season are reported. Aspergillosis was found in house sparrows ( Passer domesticus ) on two occasions.
Some supplementary records of birds in Baja California, Mexico
No abstract available.
Nesting associations between passerines and birds of prey in central North Dakota
No abstract available.
Seasonal changes in bird communities of the chaparral and blue-oak woodlands in central California
No abstract available.
[Book review] A field guide to the birds of Hawaii and the tropical Pacific by H. Douglas Pratt, Phillip L. Bruner, and Delwyn G. Berrett
No abstract available.
Trends and effects of organochlorine residues on Oregon and Nevada wading birds, 1979-83
The incidence of DDT (parent compound) declined significantly in the eggs of Black-crowned Night-Herons (Nycticorax nycticorax), White-faced Ibis (Plegadis chihi), and Black-necked Stilts (Himantopus mexicanus), and showed a downward trend in Snowy Egrets (Egretta thula). Mean DDE residues (breakdown product of DDT) in eggs declined significantly in Black-crowned Night-Herons and showed a downward trend in Black-necked Stilts and Snowy Egrets; however, no trend was apparent for White-faced Ibis. Some night-herons, egrets, and ibis laid thin-shelled eggs that cracked; eggshell thickness was negatively correlated with DDE residues in the egg contents. Ibis were the most sensitive species to DDE- induced shell thinning. Generally, reduced reproductive success for ibis started at lower DDE egg residues (3 ppm) than for either Snowy Egrets (5 ppm) or night-herons (8 ppm). Egg residue profiles, band recoveries, biotelemetry studies, and residues in fish and other prey items implicate the southwestern United States (a wintering area) as an important source of DDT-DDE that caused the most serious reproductive problem encountered during the study (in night-herons nesting at Ruby Lake, Nevada). Available evidence indicates that the three other species, together with night- herons from Oregon and Idaho, winter in Latin America.