Gray Catbird Dumetella carolinensis This information was scanned from The Birds of British Columbia (Campbell et al.), Volume III, pages 430-435. Volumes I, II and III of The Birds of British Columbia, can be ordered electronically at: orders@ubcpress.ubc.ca from UBC Press in Vancouver, British Columbia.

 

Range Gray Catbird breeds from the southern mainland of British Columbia, the southern half of the Canadian Prairie provinces, southern Ontario, southwestern Quebec, New Brunswick, Prince Edward Island, and Nova Scotia south through Washington, eastern Oregon, Utah, and eastern Texas, east to the Atlantic coast. Winters mainly on the coastal fringe of the Gulf coast and eastern Mexico, south to Panama and the Caribbean islands.

Status On the coast, rare to uncommon migrant and summer visitant locally to the lower Fraser River valley, Squamish River valley, Pemberton valley, and Bella Coola River valley; casual elsewhere on the coast. In the interior, an uncommon migrant and summer visitant to the Southern Interior, Southern Interior Mountains, and Central Interior ecoprovinces, except locally fairly common in the Okanagan valley and in the vicinity of Williams Lake; further north, a casual summer visitant in the SubBoreal Interior and the Boreal Plains ecoprovinces; casual in winter in the Southern Interior, accidental in the Southern Interior Mountains.

Status Change No change.

Nonbreeding The Gray Catbird is sparsely but widely distributed across the interior of southern British Columbia north to Quesnel and Golden, and from the southern Rocky Mountains west to Riske Creek in the Cariboo and Chilcotin areas and casually in the Fraser Lowland on the south coast. In addition, there are several occurrence records from outside the known breeding range, including Sechelt, Comox, Bella Coola, Kitimat, Hazelton, Kleena Kleene, Bowron Lake, and Fort St. John. The Gray Catbird has been recorded from sea level to 150 m on the coast and between 270 and 2,050 m in the interior. It is most abundant in riparian thickets or in open deciduous forests with an understorey of dense deciduous shrubs, small trees, and scattered conifers. Preferred habitats are thickets along the edges of streams, lakes, and ponds, fencelines, roadsides, ditches and woodland edges, and shrub-choked gullies on sagebrush-grassland slopes. Closed forest habitats are avoided. Vegetation in preferred habitat often includes clustered wild rose, red-osier dogwood, saskatoon, willows, water birch, black hawthorn, choke cherry, trembling aspen, and Oregon-grape. Human-influenced habitats include shrubby gardens and vine-tangled hedgerows along orchards and farm fields, often with Himalayan blackberry on the coast. Gray Catbirds rarely venture far from dense cover. They are heard more often than seen, and are one of the few songbirds in British Columbia that frequently sing at night. Detection of non-singing birds is difficult; thus, birds may be present, but silent, before territorial activities are detected. Apparent spring migration begins relatively late, normally from mid to late May, although in some years early migrants arrive in mid to late April. In the Okanagan valley, 28 of 37 first-of-year records occurred between 21 May and 1 June, with a mean and median date of 23 May (Cannings et al. 1987). In the south, migration peaks from late May to early June and ends abruptly. In the Williams Lake area, at the northern edge of its range, the earliest Gray Catbird arrivals are in mid-May, but few are seen until June. The autumn migration occurs mainly in late August and early September. Information on autumn departures is scarce, but by mid-September few catbirds are reported. In some years, small numbers may remain into early October in southern areas. Migratory movements are inconspicuous, as catbirds are secretive. From evidence of large numbers of catbirds killed by colliding with tall structures, such as lighthouses and tall buildings, Root (1988) concluded that it is a night migrant. The only winter occurrences are individuals at Nakusp, Irish Creek near Vernon, and Vaseux Lake. The Gray Catbird has been recorded regularly in British Columbia from 10 April to 15 October.

Breeding Nests Eggs Nest Success The Gray Catbird is a distinctive member of the summer avifauna in the warm southern valleys of the interior of British Columbia. Its highest breeding densities are in the Okanagan, Similkameen, and South Thompson river valleys; it is slightly less abundant in the valleys of the Kootenay and Columbia rivers. In the interior, nesting has been confirmed north to Wasa, Revelstoke, Horsefly Lake, and Williams Lake, and west to the Chilcotin River in the vicinity of Riske Creek. The Gray Catbird also regularly breeds in the riparian thickets along the Fraser River between Lytton and Williams Lake, and in the valley of the San Jose River south of Williams Lake. It is scarce in summer elsewhere in the central portions of the interior, where breeding likely occurs north to Quesnel. On the coast, small numbers breed in the Fraser Lowland, mainly in the Pitt Meadows area. The Gray Catbird was reported as common in summer at Stuie in the Bella Coola River valley (Laing 1942), although breeding there has not been confirmed. The species reaches its highest numbers in summer in the Okanagan valley of the Southern Interior. Breeding Bird Surveys for both coastal and interior routes contain insufficient data for analysis. Breeding habitat is similar to nonbreeding habitat, but thickets including wild rose are preferred. General habitats for reported nests were natural shrub thickets (80%) and human-influenced habitats (20%), mainly gardens, orchards, vineyards, hedgerows, and uncultivated land associated with farms. In the Okanagan valley, natural sites are frequently in moist draws and riparian areas. Cannings et al. (1987) state that only 2 of 93 nests were not in deciduous shrubs or small trees; they were in dense garden firs. The Gray Catbird breeds at elevations below 100 m in the lower Fraser River valley and up to 1,100 m in the interior. Populations are small and local throughout British Columbia, with pairs widely scattered in suitable habitat. Surveys have revealed relatively dense concentrations (5 to 10 pairs) at the north end of Okanagan Lake, the west side of Vaseux Lake, the north end of Osoyoos Lake, and the east end of Williams Lake. The Gray Catbird has been recorded breeding in British Columbia between 9 May and 16 August.

Nests:  Nests are usually built in dense tangles of vegetation. Specific nest sites (n = 139) included wild rose (47%), lilac bushes (25%), tall Oregon-grape (7%), red-osier dogwood (4%), willows (4%), and 20 other species of shrubs and small trees. The nest is a bulky assemblage of coarse material. The nest cup is lined with fine grass, plant fibres, and other soft items. The most consistently used nest materials were grass (84%), twigs (44%), plant fibres (29%), rootless (21 %), and leaves (9%); a wide assortment of other materials appeared in fewer nests. The heights above ground for 156 nests ranged from 0.2 to 8 m, with 53% between 1 and 2 m. Eggs: Dates for 137 clutches ranged from 10 May to 6 August, with 55% recorded between 12 June and 2 July. Calculated dates indicate that nests may contain eggs on 9 May. Egg laying begins about a month later in the Cariboo and Chilcotin areas than in more southern areas. Some pairs, in the Okanagan valley at least, are double-brooded. The laying of first clutches peaks in early June, second clutches about 9 July (Cannings et al.1987). It is not known what proportion of second clutches followed the loss of a first clutch rather than a successful first brood. In an Ontario study, only 3 of 22 pairs that successfully raised 1 brood attempted a second, but pairs that lost the first clutch routinely attempted a second nest (Scott et al. 1988). The same study revealed a gradual decline in mean clutch size as the season progressed. Sizes of 122 clutches ranged from 1 to 6 eggs (1E-3, 2E-7, 3E-22, 4E-57, 5E-32, 6E-1), with 73% having 4 or 5 eggs. The mean clutch size in British Columbia was 3.8 eggs (n = 124 clutches visited 2 or more times), which was almost identical to the average number of 3.9 eggs per clutch laid in Ontario between 13 May and 2 June (n = 53) (Scott et al. 1988). Both Canadian studies revealed larger clutch sizes than those recorded from Michigan, which averaged 3.3 eggs (n = 22 clutches of 2 or more). The primary difference was in the large component of five-egg clutches in British Columbia (25%), whereas no clutches over four eggs were found in Michigan (Zimmerman 1963). The incubation period in British Columbia was 12 to 15 days (n = 11). Nest Success: Of 59 nests found with eggs and followed to a known fate, 37 produced at least 1 young, for a success rate of 63%. The success rate in Michigan was 61% (n = 23) (Zimmerman 1963). In British Columbia, predation on eggs or young was suspected in 17 cases, although confirmation was lacking. Reported predators included squirrel or chipmunk (11 nests), domestic cat (3 nests), shrew, gopher snake, and American Crow (1 nest each). Heavy rain was thought to have caused the death of 1 brood. Young: Dates for 108 broods ranged from 15 June to 16 August, with 54% recorded between 1 and 20 July. Sizes of 94 broods ranged from 1 to 5 young (1Y-4, 2Y-12, 3Y-18, 4Y45,5Y-15), with 67% having 3 or 4 young. The nestling period in British Columbia was 12 to 15 days (n = 10). Family groups remained together for a short time after the young left the nest. Brown-headed Cowbird Parasitism: In British Columbia, 5% of 183 nests found with eggs or young were parasitized by the cowbird. None of eight coastal nests was parasitized. Most of the parasitism occurred in the Southern Interior, but the overall rate of 6% was higher than the 4% reported for the Okanagan valley (Cannings et al.1987). In southern Ontario, Peck and James (1987) reported a parasitism rate of 1.5% (n = 1,193), although they were careful to mention that the percentage of attempted parasitism was undoubtedly higher. Three parasitized nests were closely observed in British Columbia. In each, the cowbird egg(s) disappeared from the nest within 2 days. A catbird from 1 nest that had received 2 cowbird eggs was seen carrying a cowbird egg in its beak, and both eggs were missing from the nest a day after they were deposited. The Gray Catbird is known to routinely eject cowbird eggs within a day after they are laid (Nickel 1958; Friedmann 1963; Rothstein 1975; Scott 1977). The latter author suggested that the attentiveness of the Gray Catbird, and its vigorous defence of the nest, made it difficult for cowbirds to lay their eggs and remove 1 or more eggs of the host. In British Columbia, there is a record of a cowbird nestling together with a catbird nestling, but there are no records in British Columbia of the catbird fledging a cowbird. Elsewhere there are a few cases of successful parasitism (Woodward 1976; Lowther 1980).

Remarks The Gray Catbird was formerly known as Catbird. Belles-Isles and Picman (1986c) report that the Gray Catbird destroyed a variety of eggs of other species placed near the nest. For additional information on breeding biology and on distinguishing age and sex, see Bent (1948), Nickell (1965), Johnson and Best (1980), and Suthers and Suthers (1990).