. The Canadian field-naturalist. 1999 Butler: Shorebirds and Songbirds on the Fraslr River Delia 391. Figure L Location of study area (shaded) on the Eraser River delta, British Columbia. crabapple {Malus sp.), intermixed with trees spaced at most every 50 m. The predominant tree species were Trembling Aspen (Populiis tremuloides) and Cottonwood (P. balsamifera). The understory shrub layer was mostly rose, blackberry, and Snowberry (Symphoricarpiis albus). Tree height in tree- hedgerows ranged from about 6-25 m. Bird abun- dance was estimated by recording all birds heard or seen during 12-minu
. The Canadian field-naturalist. 1999 Butler: Shorebirds and Songbirds on the Fraslr River Delia 391. Figure L Location of study area (shaded) on the Eraser River delta, British Columbia. crabapple {Malus sp.), intermixed with trees spaced at most every 50 m. The predominant tree species were Trembling Aspen (Populiis tremuloides) and Cottonwood (P. balsamifera). The understory shrub layer was mostly rose, blackberry, and Snowberry (Symphoricarpiis albus). Tree height in tree- hedgerows ranged from about 6-25 m. Bird abun- dance was estimated by recording all birds heard or seen during 12-minute stops at eight stations spaced at 75-m intervals along hedgerows about once each week for 20 days between 22 October 1990 and 31 March 1991. I also noted the habitat (hedgerow, farm field, or beach) in which mobile avian preda- tors were first detected during shorebird and song- bird censuses. Results Fewer Dunlin and Black-bellied Plovers were in fields than roosted on the beaches of Boundary Bay. The median size of 28 roosting flocks on beaches was 6450 birds (900-12 000) compared to 507 birds (8-7900) in 48 farmland roosting flocks. The great- est numbers of shorebirds recorded in farmlands on a single day was 11600 Dunlin on 9 November 1990 and 7108 plovers on 27 October 1990. Dunlin and plovers in fields were mostly foraging between November and March (Table 1). Dunlin and plovers that departed from the beaches settled in fields throughout the km band of farmland north of Boundary Bay (Table 2). I detected 45 species of songbirds in hedgerows of which 28 species were common to both shrub- and tree-hedgerows (Tables 3 and 4). Shrub-hedgerows supported fewer species and a lower abundance of songbirds than tree-hedgerows; 30 species with an average of individuals per station were detected in shrub-hedgerows compared to 40 species with an average of individuals per station in tree-hedge- row. Song Sparrow. American Robin and White- crowned Sparrow made up ove
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