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Barred Owl Nesting on the Ground

1959; Oxford University Press; Volume: 76; Issue: 2 Linguagem: Inglês

10.2307/4081780

1938-4254

W.B. Robertson,

Avian ecology and behavior

Barred Owl Nesting on the Ground.--OnJanuary 6, 1957, Ralph Johnston, lookout at Seven-Mile Fire Tower, Everglades National Park, sent me word that a Barred Owl (Strix varia) had established a nest on the ground at the foot of the tower.Despite its exposed situation, the nest was maintained until the three eggs hatched in early February, the nestlings surviving for about one week.The nest's unusual location and the extreme tameness of the parent birds gave opportunity for more satisfactory observation than is ordinarily possible at Barred Owl nests.At my suggestion, Johnston entered his daily observations in the tower log, and Fred K. Truslow devoted a number of days to watching the nest and obtained an excellent series of photographs.!am greatly indebted to Messrs. Johnston and Truslow for permission to report information that they recorded.Nest Site: Seven-Mile Fire Tower is located in the open Everglades of Dade County, Florida (Section $0, Township 55S, Range $6E), seven miles south of the Tamiami Trail (U.S. Route 41) at a point about $5 miles west of Miami.The tower site is a two-acre fill enclosed by a canal, and the tower itself is of open steel frame construction 85 feet high.The nest was placed within the base of the tower behind a concrete block that forms the bottom step of the first flight of stairs.The step may have afforded some shelter to the nest at the northwest side but, because of their location and angle of ascent, the stairs provided neither overhead cover nor shade.The site had been newly mowed at the time the nest was established, and the incubating adult was in no way concealed or enclosed (Plate 7, Below).Bent (1958: 185) reported that Barred Owls may devote considerable effort to lining and reshaping nests when they utilize old nests of hawks or squirrels, but in the present case no attempt at nest-building was evident.The eggs were laid in a very shallow oval depression (about 10" x 6"), apparently a natural irregularity in the ground surface, and the sparse nest-lining consisted only of lawn clippings that were at the site and still-rooted grasses matted down during the course of incubation.Nest Chronology: In his five previous winter seasons as a lookout, Johnston had often seen and heard Barred Owls around Seven-Mile Fire Tower.During November and December 1956, two owls consistently frequented the immediate area and were seen a number of times in full daylight, either perched on the framework of the tower or on the ground beneath it near the eventual nest site.About 6:00 p.m. on January 5, one held its position at the foot of the tower as Johnston walked by within a few feet, and it was still there later that evening.At 9:30 a.m. on January 6, the bird was seen to leave, and a check of the spot showed that one egg had been deposited.The date of the first egg (probably January 5) indicates a rather early nesting, the earliest date in 22 Florida records summarized by Bent (1938: 197) being January 11.Howell (1932: 295), however, recorded Barred Owl egg dates in Florida as early as December 25.The course of events at the nest after January 6 was as follows-January 7, second egg laid; seen in the evening, only one present earlier in the day.January to, third egg suspected at 9:00 a.m., but the full clutch of three not seen until the nest was vacated briefly after dark on January 14.February 7, three eggs still unhatched at dusk.February 8, one egg shell seen beside the bird on the nest at 7:$0 a.m., the first indication of hatching.Morning of February 9, another egg shell visible beside the sitting bird.(In both instances, the shells disappeared shortly, but the method of disposing of them was not