Crop-milk cycles in band-tailed pigeons and losses of squabs due to hunting pigeons in September Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rn301370v

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  • The production of crop-milk in band-tailed pigeons was investigated to estimate losses of squabs that occur from hunting pigeons during September.¹ Living birds held captive were examined with a cystos cope and pigeons killed by hunters were examined in the field to determine changes in gross appearance of crops and the timing of these changes through the reproductive cycle. Two cycles in the production of crop-milk were found, a daily cycle and a seasonal cycle. The seasonal cycle extended from the time an egg was laid, through fledging of the squab, until an egg in the next cycle was laid. Four phases were identified in the seasonal cycle; inactive, developing, active and regressing. Crop-milk was produced during the active phase in a daily cycle for approximately 30 days. The daily cycle had five characteristic phases, but crop-milk was found in only two or three, indicating that crop-milk was not a consistent criterion for identifying pigeons with active crops. Daily cycles of crops of males and females appeared not to be synchronized. Sixty-two percent of 614 pigeons killed by hunters had active crops, 31 percent were inactive, 5 percent were regressing and 2 percent were developing. The ability of one parent to fledge a squab was determined by removing the other parent at various stages of incubation and brooding. Squabs could not be fledged in the normal length of time (22 to 24 days of brooding) by one parent if the other parent was removed prior to the 9th day of brooding. Losses of productivity that occurred from hunting pigeons in Oregon during September were estimated using two methods. Minimal estimates were 3.5 percent and 5. 0 percent, and the maximal estimates were 5. 8 percent and 7. 2 percent, respectively. These data indicated that hunting pigeons in September may not affect productivity of these populations significantly. ¹ [This study was supported by the Bureau of Sport Fisheries and Wildlife, U. S. Fish and Wildlife Service, and the Oregon Agricultural Experiment Station, Corvallis.]
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  • description.provenance : Approved for entry into archive by Katy Davis(kdscannerosu@gmail.com) on 2014-01-30T16:07:04Z (GMT) No. of bitstreams: 1 ZeiglerDonL1971.pdf: 2296733 bytes, checksum: 081c09f6c5cfb2071546b7a454e5b898 (MD5)
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