Sora (<i>Porzana carolina</i>) Parasitism of Red-winged Blackbird (<i>Agelaius phoeniceus</i>) Nests

Sora (Porzana carolina) is a conspecific brood parasite that also occasionally parasitizes nests of other species. Sora parasitism in nests of passerines is rare. Of 129 Red-winged Blackbird (Agelaius phoeniceus) nests found in North Dakota in 2009 and 2010, two (1.6%) were parasitized by Soras. The conditions favouring this rare parasitic behaviour may include competition for nest sites and high Sora density.

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The time of day of egg laying by the Brown-headed Cowbird and other icterines

Canadian Journal of Zoology ◽

10.1139/z91-292 ◽

1991 ◽

Vol 69 (8) ◽

pp. 2093-2099 ◽

Cited By ~ 61

Author(s):

David M. Scott

Keyword(s):

Molothrus Ater ◽

Time Of Day ◽

Egg Laying ◽

Agelaius Phoeniceus ◽

Brood Parasite ◽

Dendroica Petechia ◽

Cardinalis Cardinalis ◽

Vireo Olivaceus ◽

Molothrus Bonariensis ◽

Dumetella Carolinensis

I present data on the time of day of oviposition for 16 species of icterines to evaluate the idea that laying exceptionally early in the morning by the brood parasite, the Brown-headed Cowbird (Molothrus ater), is a specialization for parasitism. This cowbird, the earliest known layer among icterines, typically lays before sunrise (sunrise −9.14 ± 2.52 (SE) min, n = 36). Another brood parasite, the Shiny Cowbird (Molothrus bonariensis), also sometimes lays before sunrise. The best-known nonparasitic icterines, the Red-winged Blackbird (Agelaius phoeniceus) and the Common Grackle (Quisacalus quiscula), lay shortly after sunrise. Fragmentary records show that several other icterines lay within an hour or so after sunrise. Data are inadequate to conclude that early laying by Brown-headed Cowbirds has arisen as an adaptation for parasitism. The Brown-headed Cowbird at London, Ontario, lays earlier than most local passerines, as is shown by new data on oviposition by seven host species arranged in order of increasing lateness of oviposition: Agelaius phoeniceus, Dendroica petechia, Melospiza melodia, Cardinalis cardinalis, Vireo olivaceus, Dumetella carolinensis, and Turdus migratorius.

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Landscape Composition Encompassing Cooper's Hawk Nest Sites in Western North Dakota

Journal of Raptor Research ◽

10.3356/0892-1016-55.1.93 ◽

2021 ◽

Vol 55 (1) ◽

Author(s):

Janelle M. Taylor ◽

Robert N. Rosenfield ◽

Robert K. Murphy ◽

David A. Grosshuesch

Keyword(s):

North Dakota ◽

Landscape Composition ◽

Nest Sites ◽

Western North Dakota

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Territory dynamics and patterns of female recruitment in Red-winged Blackbirds (Agelaius phoeniceus)

Canadian Journal of Zoology ◽

10.1139/z87-072 ◽

1987 ◽

Vol 65 (3) ◽

pp. 465-471 ◽

Cited By ~ 8

Author(s):

T. E. Dickinson ◽

M. R. Lein

Keyword(s):

Mating Systems ◽

Nest Site ◽

Active Role ◽

Territory Size ◽

Agelaius Phoeniceus ◽

Nest Sites ◽

Harem Size ◽

Nesting Sites ◽

Territory Dynamics

The territorial boundaries defended by male Red-winged Blackbirds (Agelaius phoeniceus) shifted over the course of the breeding season. The establishment of new males in a colony, the redefinition of boundaries among neighbors, and the recruitment of new females were all related to changes in boundary locations. No significant correlations were found between harem size and either territory size or the abundance of preferred nesting sites. High rates of aggressive interactions did, however, coincide with the recruitment of new females and accompanied territory shifts. Many boundary changes were associated with the guarding by males of females that were showing interest in nest sites outside the area formerly defended by the male. If a female's behavior in an area precipitates conflicts among neighboring males, then it could be a mechanism whereby females simultaneously compare the attributes of males and influence the quality of their territories. Such a mechanism would ensure that a female obtains what she has determined to be the best available nest site and a male that can defend her choice. A more active role for females should be included in models of the evolution of mating systems.

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Reproductive success is a misleading indicator of nest-site preferences in the Red-winged Blackbird

Canadian Journal of Zoology ◽

10.1139/z98-180 ◽

1998 ◽

Vol 76 (12) ◽

pp. 2227-2234 ◽

Cited By ~ 2

Author(s):

Stanislav Pribil

Keyword(s):

Reproductive Success ◽

Site Selection ◽

Nest Site ◽

Nest Site Selection ◽

Agelaius Phoeniceus ◽

Erroneous Conclusion ◽

Nest Sites ◽

Site Preferences ◽

Limited Variation ◽

Nest Site Preferences

Several methods are used to detect nest-site preferences of birds. One method postulates that individuals will prefer those nest-site features that increase their reproductive success. To determine which features affect reproductive success, and hence should be preferred, the method examines correlations between reproductive success and various nest-site features. When a statistically significant correlation is found, it is concluded that individuals exhibit a preference for that feature. In the absence of a correlation, it is concluded that individuals are indifferent to the feature. Here, I argue that this method may lead to misleading conclusions. If good sites are abundant, all individuals should choose them. Consequently, there will be little variation in the features of the chosen sites. This limited variation, when related to reproductive success, may fail to yield a statistically significant correlation and thus lead to the erroneous conclusion that individuals have no preference. An alternative method of detecting nest-site preferences is to compare features of chosen sites with features of available sites. In this study, I used both methods to investigate nest-site selection in the Red-winged Blackbird (Agelaius phoeniceus). I compared vegetation features of nest sites with those of randomly selected sampling sites and found significant differences. The differences imply that Red-winged Blackbirds prefer vegetation that grows in small patches and is tall and sparse, and the plants have thick stems. I found no relationship between these vegetation features and reproductive success. These results suggest that Red-winged Blackbirds have strong preferences for certain vegetation features, but these preferences cannot be detected from correlations with reproductive success.

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