Male Incubation and Multiple Brooding in Sagebrush Brewer's Sparrows

Mahony, Nancy A.; Haegen, W. Matthew Vander; Walker, Brett L.; Krannitz, Pamela G.

doi:10.1676/0043-5643(2001)113[0441:miambi]2.0.co;2

Cited by 13 publications

(10 citation statements)

References 11 publications

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“…We found that constancy was significantly greater at biparental nests, a pattern evident in other songbirds with male incubation (Matysioková and Remeš ). The proportions of biparental nests at our high‐elevation study sites (Badger Mountain 50%, Bald Mountain 92%) were greater than previous estimates from the northern periphery of the species’ range where Brewer's Sparrows breed at lower elevation (24–32% in British Columbia, 30–56% in Washington; Mahony et al ). The true proportion of biparental nests in our study may have been even higher because our method of detecting the behavior was susceptible to Type II errors.…”

Section: Discussioncontrasting

confidence: 77%

“…Marking a sample of birds was logistically impossible, so we conducted a case study of a biparental nest at Badger Mountain by marking the head of a color‐banded male with a non‐toxic marker that was thereafter visible in the camera view. We noticed that the male and female incubated in an alternating pattern (as reported by Mahony et al ), and both adults were occasionally seen on the screen together during transitions (Fig. A).…”

Section: Methodssupporting

confidence: 79%

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Biparental incubation and allofeeding at nests of Sagebrush Brewer's Sparrows

2015

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ABSTRACT. Facultative male incubation and allofeeding are thought to be behavioral adaptations by which male songbirds maximize their fitness by reducing the energetic stress of their mates. However, few data are available for most species that exhibit these behaviors so the extent to which they might enhance male fitness remains unclear. Among North American sparrows, male incubation is known in four species, but the relative contributions of each sex have been estimated for only one species. We quantified biparental incubation and allofeeding in Sagebrush Brewer's Sparrows (Spizella breweri breweri) with 24-h video surveillance of nests (N = 24) at two locations in northern Nevada. We detected biparental incubation at both sites (17 of 24 nests, 71%), and found that mean constancy (i.e., proportion of 24-h period eggs were covered) was significantly higher at biparental nests than at uniparental nests, and mean recess duration (i.e., when eggs were uncovered) was significantly shorter. Incubation constancy at biparental nests in our study was the highest yet reported in the genus Spizella (range = 0.87-0.96), and constancy at uniparental nests (mean = 0.76, range = 0.71-0.81) was greater than that of congeners where female-only incubation is thought to be the norm. Biparental incubation was more likely on colder days, but a comparison of models where incubation strategy and its interaction with ambient temperature were included as independent variables revealed that temperature was not the best predictor of constancy. Allofeeding occurred at very low frequency and only at biparental nests (11 of 20, 55%). Biparental nests with allofeeding had more incubation sessions per hour than biparental nests without allofeeding. The recipient usually left the nest immediately after being fed, and the feeding individual assumed the role of incubator. Our results suggest that some factor other than low ambient temperatures favors biparental incubation by Sagebrush Brewer's Sparrows. One possibility is that male incubation and the resulting increase in incubation constancy may better conceal nests and reduce the likelihood of nest predation. The low frequency of allofeeding at nests with biparental incubation in our study suggests that it serves some function other than improving female nutritional status or reducing activity levels at nests. Rather, allofeeding may serve as an intraspecific signal important for maintaining the social bond between mates.RESUMEN. Incubación biparental y alo-alimentación en nidos de Spizella breweri Se cree que la incubación facultativa y la alo-alimentación son adaptaciones del comportamiento mediante las cuales los machos de las aves maximizan su aptitud mediante la reducción de estrés energético de sus parejas. Sin embargo, existen pocos datos disponibles para la mayoría de las especies que exhiben estos comportamientos, por lo que la magnitud a la cual pueden incrementar la aptitud del macho es aún desconocida. Entre los gorriones de Norte América, la incubación por parte del macho es cono...

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Section: Discussioncontrasting

confidence: 77%

Section: Methodssupporting

confidence: 79%

Biparental incubation and allofeeding at nests of Sagebrush Brewer's Sparrows

2015

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“…The percentage of pairs fledging young on her sites (all were in continuous habitat) was similar to that on my continuous sites (87% in both studies); however, she reported a somewhat higher percentage of pairs fledging additional nests (38% vs. 25%). In a study in British Columbia, Canada (Mahony et al 2002), investigators followed Brewer's Sparrow pairs on four sites in largely unfragmented habitat, documenting all nesting attempts of 176 colorbanded pairs. Again, my results from continuous sites in Washington were similar to the British Columbia findings for percentage of pairs fledging young (79% vs. 70%), but somewhat lower for the percentage of pairs going on to fledge additional nests (7% vs. 18%).…”

Section: Discussionmentioning

confidence: 99%

Fragmention by Agriculture Influences Reproductive Success of Birds in a Shrubsteppe Landscape

Haegen

2007

Ecological Applications

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Shrubsteppe communities are among the most imperiled ecosystems in North America as a result of conversion to agriculture and other anthropogenic changes. In the Intermountain West of the United States, these communities support a unique avifauna, including several species that are declining and numerous others that are of conservation concern. Extensive research in the eastern and central United States and in Scandinavia suggests that fragmentation of formerly continuous forests and grasslands adversely affects reproductive success of birds, yet little is known of the potential effects on avian communities in Western shrublands. I used multi-model inference to evaluate the potential effects of local and landscape variables on nest predation and brood parasitism, and behavioral observations of color-banded birds to evaluate the potential effects of habitat fragmentation on seasonal reproductive success of passerines in the shrubsteppe of eastern Washington State, USA. Reproductive success of shrubsteppe-obligate passerines was lower in landscapes fragmented by agriculture than in continuous shrubsteppe landscapes. Daily survival rates for nests of Brewer's Sparrows (Spizella breweri; n=496) and Sage Thrashers (Oreoscoptes montanus; n=128) were lower in fragmented landscapes, and seasonal reproductive success (percentage of pairs fledging young) of Sage Sparrows (Amphispiza belli; n=146) and Brewer's Sparrows (n=59) was lower in fragmented landscapes. Rates of parasitism by Brown-headed Cowbirds (Molothrus ater) overall were low (4%) but were significantly greater in fragmented landscapes for Brewer's Sparrows, and parasitism resulted in fewer young fledged from successful nests. Simple models of population growth using landscape-specific fecundity and estimates of adult survival derived from return rates of banded male Sage Sparrows and Brewer's Sparrows suggest that fragmented shrubsteppe in Washington may be acting as a population sink for some species. Immediate conservation needs include halting further fragmentation of shrubsteppe, restoring low-productivity agricultural lands and annual grasslands to shrubsteppe where possible, and convincing the public of the intrinsic value of these imperiled ecosystems.

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“…Possible reasons for multiple brooding might be an unusually long breeding season, a small first brood, nest success, food supply, age, and experience (Smith 1982, Roth and Johnson 1993, Friesen et al 2000, Mahony et al 2001, Friesen et al 2001; however, the reason for triple brooding in this female is unclear. In BC, in isolated riparian patches of habitat where the female bred, the mean clutch size during 2002 and 2003 was 3.75 and 3.57 (Morgan et al 2007).…”

mentioning

confidence: 95%

“…Double brooding in Wood Thrushes was much higher, at least 74%, but could be as high as 87% if unidentified females were included (Friesen et al 2000). In the south Okanagan Valley at the northern edge of the range for Sagebrush Brewer's Sparrows (Spizella breweri breweri) distribution, 17% of females had double broods and two females had triple broods (Mahony et al 2001).…”

mentioning

confidence: 98%