Cowbird (Molothrus spp.) Ecology: A Review of Factors Influencing Distribution and Abundance of Cowbirds across Spatial Scales

Chace, Jameson F.; Farmer, Chris; Winfree, Rachael; Curson, David R.; Jensen, William E.; Goguen, Christopher B.; Robinson, Scott K.

doi:10.2307/40166814

Cited by 41 publications

(63 citation statements)

References 81 publications

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confidence: 99%

“…The frequencies of cowbird parasitism appear to follow a similar biogeographical pattern (e.g., Smith and Myers-Smith 1998), especially for grassland birds Cully 2005a, 2005b), although this relationship may not be generalized across habitats (Robinson and Smith 2000) and may not be indicative of parasitism frequencies at the local level (Chace et al 2005). Nonetheless, Chace et al (2005) acknowlBrown-headed Cowbird, Molothrus ater, Parasitism and Abundance in the Northern Great Plains edged that, at the continental scale, cowbird abundance appears to be a reasonable predictor of cowbird parasitism levels. Because of the difficulty in obtaining data on both cowbird abundance and brood parasitism across the continent (or even over a large region), there are few examples of studies that have evaluated this relationship using cowbird and nest data collected concurrently at the same study sites over a large region (e.g., Cully 2005a, 2005b).…”

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confidence: 99%

“…That is, given that cowbirds are host generalists, measures of avian abundance or richness might serve as proximate cues for cowbirds in determining where to settle (McGeen 1972;Farmer 1999). Chace et al (2005) listed four nested levels of an avian community that cowbirds could use as cues for settlement: (1) all breeding birds in the avian community, (2) all passerine species, (3) all host species, and (4) a single host species. Very few studies have evaluated this relationship at all four levels (Farmer 1999).…”

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confidence: 99%

“…Using BBS (Breeding Bird Survey) data, Hahn and O'Connor (2002) concluded that cowbird distribution was not simply the result of shared habitat preferences with their hosts, but rather host abundance was an important predictor of cowbird occurrence in recently colonized regions of the United States (i.e., eastern and western states) and to a lesser extent in the cowbird's ancestral range (i.e., central Great Plains). Except for Hahn and O'Con nor's (2002) evaluation using BBS data, the influences of avian abundance and richness on cowbird distribution and abundance have not been evaluated using regional data from the northern Great Plains (reviewed in Chace et al 2005).…”

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confidence: 99%

“…Several host species are known to avoid or reduce parasitism by acting aggressively toward cowbirds Norman 1976, 1977), but aggression is not always an effective host defense against cowbird parasitism, especially in habitats in which host densities are low because cowbirds may use host aggression (Robertson and Norman 1977) or vocalizations (Clotfelter 1998) to locate nests. Nonetheless, the Red-winged Blackbird is one of a few species reported to reduce parasitism by mobbing (Freeman et al 1990;Chace et al 2005).…”

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Brown-headed Cowbird, <em>Molothrus ater</em>, Parasitism and Abundance in the Northern Great Plains

Igl

Johnson

2007

Can Field Nat

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The Brown-headed Cowbird (Molothrus ater) reaches its highest abundance in the northern Great Plains, but much of our understanding of cowbird ecology and host-parasite interactions comes from areas outside of this region. We examine cowbird brood parasitism and densities during two studies of breeding birds in the northern Great Plains during 1990–2006. We found 2649 active nests of 75 species, including 746 nonpasserine nests and 1902 passerine nests. Overall, <1% of nonpasserine nests and 25% of passerine nests were parasitized by Brown-headed Cowbirds. Although the overall frequency of cowbird parasitism in passerine nests in these two studies is considered moderate, the frequency of multiple parasitism among parasitized nests was heavy (nearly 50%). The mean number of cowbird eggs per parasitized passerine nest was 1.9 ± 1.2 (SD; range = 1–8 cowbird eggs). The parasitism rates were 9.5% for passerines that typically nest in habitats characterized by woody vegetation, 16.4% for grassland-nesting passerines, 4.7% for passerines known to consistently eject cowbird eggs, and 28.2% for passerines that usually accept cowbird eggs. The Red-winged Blackbird (Agelaius phoeniceus) was the most commonly parasitized species (43.1% parasitism, 49.6% multiple parasitism, 71.2% of all cases of parasitism). Passerine nests found within areas of higher female cowbird abundance experienced higher frequencies of cowbird parasitism than those found in areas of lower female cowbird abundance. Densities of female cowbirds were positively related to densities and richness of other birds in the breeding bird community.

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Brown-headed Cowbird, <em>Molothrus ater</em>, Parasitism and Abundance in the Northern Great Plains

Igl

Johnson

2007

Can Field Nat

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Projecting avian response to linked changes in groundwater and riparian floodplain vegetation along a dryland river: a scenario analysis

Brand

Stromberg

Goodrich³

et al. 2011

Ecohydrology

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Groundwater is a key driver of riparian condition on dryland rivers but is in high demand for municipal, industrial, and agricultural uses. Approaches are needed to guide decisions that balance human water needs while conserving riparian ecosystems. We developed a space-for-time substitution model that links groundwater change scenarios implemented within a Decision Support System (DSS) with proportions of floodplain vegetation types and abundances of breeding and migratory birds along the upper San Pedro River, AZ, USA. We investigated nine scenarios ranging from groundwater depletion to recharge. In groundwater decline scenarios, relative proportions of tall-canopied obligate phreatophytes (Populus/Salix, cottonwood/willow) on the floodplain progressively decline, and shrubbier species less dependent on permanent water sources (e.g. Tamarix spp., saltcedar) increase. These scenarios result in broad shifts in the composition of the breeding bird community, with canopynesting and water-obligate birds declining but midstory nesting birds increasing in abundance as groundwater declines. For the most extreme draw-down scenario where all reaches undergo groundwater declines, models project that only 10% of the upper San Pedro floodplain would be comprised of cottonwood/willow (73% saltcedar and 18% mesquite), and abundances of canopy-nesting, water-obligate, and spring migrant birds would decline 48%, 72%, and 40%, respectively. Groundwater recharge scenarios were associated with increases in canopy-nesting birds particularly given the extreme recharge scenario (all reaches regain shallow water tables and perennial streamflow). Model outputs serve to assess the sensitivity of biotic groups to potential changes in groundwater and thus to rank scenarios based on their expected ecological impacts.

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Reducing the conservation reliance of the endangered Kirtland's warbler through adaptive management

2019

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Species are considered conservation‐reliant when their continued existence is dependent on human assistance. Conservation reliance challenges the conservation community in terms of their ability to sustain the funding and public‐private partnerships needed for indefinite management. Although increased funding for conservation is critical, reducing conservation reliance through adaptive management represents an attractive alternative. We used a large‐scale ecological experiment as a case study in the use of adaptive management to reduce conservation reliance. For >40 years, the United States Fish and Wildlife Service has trapped and lethally removed an obligate brood parasite, the brown‐headed cowbird (Molothrus ater), to protect the Kirtland's warbler (Setophaga kirtlandii) from the negative effects that brood parasitism has on its reproductive success. To determine if the conservation reliance of the Kirtland's warbler could be reduced through optimization of the cowbird control program, we used an adaptive management approach. In collaboration with stakeholders, we experimentally reduced cowbird trapping effort across nearly all of the Kirtland's warbler breeding range. We monitored the resulting cowbird abundance and rate of parasitism, and then adjusted the scale of trap reductions based on the previous year's results. Despite reducing (2015–2017) and eventually eliminating (2018) cowbird trapping, we detected only 20 cowbirds (2015–2017) and found that just 4 of 514 (<1%) nests were parasitized (2015–2018). Our results indicate that the cowbird control program can at least temporarily be suspended, thereby reducing conservation reliance in the Kirtland's warbler and freeing funds for other management. We urge the conservation community to consider the use of adaptive management to reduce conservation reliance in other threatened and endangered taxa. © 2019 The Wildlife Society.

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Cowbird (Molothrus spp.) Ecology: A Review of Factors Influencing Distribution and Abundance of Cowbirds across Spatial Scales

Cited by 41 publications

References 81 publications

Brown-headed Cowbird, <em>Molothrus ater</em>, Parasitism and Abundance in the Northern Great Plains

Brown-headed Cowbird, <em>Molothrus ater</em>, Parasitism and Abundance in the Northern Great Plains

Projecting avian response to linked changes in groundwater and riparian floodplain vegetation along a dryland river: a scenario analysis

Reducing the conservation reliance of the endangered Kirtland's warbler through adaptive management

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