Date of Award

5-1-1979

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Abstract

The spring and summer ecology of female greater prairie chickens in northwestern Minnesota was intensively studied from mid-April through August during 1975, 1976, and 1977. Twenty-one females were radio-tagged and monitored for an average of 57.1 days, yielding 1,113 locations. Female visits to booming grounds peaked around 12 April and copulations peaked around 20 April. Habitats disturbed by culti vation, grazing, haying, and burning accounted for 60.6% of all loca tions of monitored females during egg laying and incubation with crop land used by 10 of 17 females. Egg laying commenced an average of 3.8 days after copulation at a rate of 1.0 egg per day for first nests. The average clutch size of 14.6 for first nests was larger than reported in other parts of the range. The incubation period of 25.5 days was longer than generally reported elsewhere and was somewhat longer for early nests than later nests. Thirty-six nests were located by moni toring radio-tagged females and by nest searching using a cable-chain drag. The average nest success for 1975-77 was 62.4%. Striped skunks and red foxes were the primary nest predators. Foxes also preyed upon 2 nesting females. Habitats undisturbed for 1 or more years were preferred for nesting. Dense, vertically oriented cover at ground level was apparently important in nest site selection, since the mean level at which 100% visual obstruction occurred using a Robel density pole was 2.0 dm. Litter depth apparently was not important in nest site selection but, along with brush clumps, tended tc be inversely related to nesting success. Brome and redtop habitats were preferred for nesting while most native types were used in relation to their availability. Six renests occurred an average of 6.4 days after nest destruction and were located a mean of 760.0 m from previous nests. Two females established nests 29.8 and 4.6 m from their successful nests of the preceding year and demonstrated "nest-slte tenacity.” Fidelity to a given booming ground was demonstrated by 4 of 5 females returning to the ground where they were trapped the preceding year. Nests were not always located closest to the booming ground where copulation occurred. Most clutches hatched between 25 May and 14 June and later clutches tended to hatch during a period receiving more pre cipitation. Mortality of radio-tagged broods was high with only 2 chicks of 11 broods alive at the end of the summer. Monitored broods made minimum movements of 1950.6 m during week 1 and 1930.6 m during week 2. Extensive early movements, heavy precipitation, lack of favor able brooding areas, and disturbance associated with radio tracking were thought to contribute tc high brood mortality. Predation of radio- tagged females was high (10 of 21) and thought to be related to in creased vulnerability due to reproductive activities and detrimental effects of radio tagging. Disturbed habitats accounted for 68.8% of young brood locations and 78.0% for late broods. Disturbed habitats accounted for 70.9% of the total locations for broodless females. The spring density of 6 males per 259.0 ha in the best portion of the study area is low in comparison to other portions of the range suggesting that the population was below the potential carrying capacity. Brood mortality was believed to be more important in limiting reproduction than nest failures. Preferred nest cover and brood cover were not the sane. A system of maintaining brood habitats by rotational dis turbance and interspersing them within nesting cover is recommended to enhance reproduction.

Download

Share

COinS