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Northern Prairie Wildlife Research Center

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Frequency of Egg and Nestling Destruction by Female Brown-headed Cowbirds at Grassland Nests

Tables

Table 1.  Host egg and nestling destruction by Brown-headed Cowbirds at grassland passerine nests monitored with miniature videocameras.
Case Date Host species Stage Days incubated or nestling age Host eggs/nestlings Number of cowbird visits Cowbird parasitisma Nest fate
When camera setup Destroyed or removed
1 28 June 1996 Western Meadowlark Incubation 6 5 5 1 None Abandonb
2   7 June 1997 Clay-colored Sparrow Incubation 6 4 3 4 None Abandonb
3 28 June 1998 Bobolink Incubation 10 4 1 4 Beforec Fledge
4 27 May 1999 Savannah Sparrow Incubation 1 4 2 3 After Abandon
5   7 June 1999 Bobolink Incubation 6 6 1 1 None  
13 June 1999   Nestling 0 5 3 1 None Fledge
6 21 June 1999 Red-winged Blackbird Incubation 6 3 2 2 Before, after Predation
7 13 July 1999  Savannah Sparrow Nestling 4 4 3 1 None Fledge
a Before = prior to camera deployment; After = after camera deployment; None = no cowbird eggs laid before or after camera deployment.
b Nest was not attended by parents after camera deployment; cowbird visits occurred on the day of camera deployment.
c Cowbird egg found outside the nest on the day of camera deployment.

 

Table 2.  Frequency of cowbird parasitism at grassland songbird nests in North Dakota, 1996-1999.
Host species

Nests found Nests with cameras
Total Parasitized (%) Total Parasitized (%)
Sedge Wren  (Cistothorus platensis) 4 0(0) 0 0(0)
Sprague's Pipit  (Anthus spragueii) 7 0(0) 0 0(0)
Common Yellowthroat  (Geothlypis trichas) 2 0(0) 1 0(0)
Clay-colored Sparrow  (Spizella pallida) 492 68(14) 64 6(9)
Vesper Sparrow  (Pooecetes gramineus) 53 0(0) 6 0(0)
Savannah Sparrow  (Passerculus sandwichensis) 150 31(21) 29 2(7)
Grasshopper Sparrow  (Ammodramus savannarum) 21 2(10) 4 1(25)
Baird's Sparrow  (Ammodramus bairdii) 11 3(27) 3 1(33)
Le Conte's Sparrow  (Ammodramus leconteii) 6 0(0) 2 0(0)
Nelson's Sharp-tailed Sparrow  (Ammodramus nelsoni) 1 0(0) 0 0(0)
Song Sparrow  (Melospiza melodia) 11 5(45) 2 1(50)
Unknown sparrow 9 3(33) 0 0(0)
Chestnut-collared Longspur  (Calcarius ornatus) 71 3(4) 9 0(0)
Bobolink  (Dolichonyx oryzivorus) 36 11(31) 8 2(25)
Red-winged Blackbird  (Agelaius phoeniceus) 4 2(50) 1 1(100)
Western Meadowlark  (Sturnella neglecta) 7 0(0) 3 0(0)
Total 885 128(14) 132 14(11)