Nest sites and reproductive success of the Barred Owls (Strix varia) in Michigan

Abstract

During 1976-1995 we monitored 114 Barred Owl (Strix varia) breeding attempts in northern Michigan. We describe nest sites and report reproductive success for different types of nest sites. Most natural nest sites were tree cavities caused by decay at places where a limb or tree top had broken off. The mean d.b.h. of cavity trees (N = 18) was 48 cm and mean cavity floor area (N = 19) 508 cm². Overall, 75 percent of breeding attempts were successful with a mean brood size (N = 75) of 1.97 young/productive nest. Owls nesting in tree cavities (N = 49) and in boxes (N = 52) showed similar productivities. While 80 percent of nests in cavities and boxes combined were productive with mean brood size (N = 81) of 2.01 young/ productive nest, only 31 percent of breeding attempts in hawk nests and other open sites (N = 13) were successful with mean brood size (N = 3) of 1.0 young/productive nest. Owlets falling from open nests prematurely, before they were able to climb, is seen as the principal cause of poor productivity. The critical importance to Barred Owls of large trees and snags with cavities is emphasized in their management.

Parent Publication

• Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium

Citation

Postupalsky, Sergej; Papp, Joseph M.; Scheller, Lewis. 1997. Nest sites and reproductive success of the Barred Owls (Strix varia) in Michigan. In: Duncan, James R.; Johnson, David H.; Nicholls, Thomas H., eds. Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium. Gen. Tech. Rep. NC-190. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 325-337.