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Figure 28.1 Relationship between annual survival of Common Sandpipers Actitis hypoleucos and mean temperature in the latter half of April, soon after arrival in breeding areas, England, 1977-1989 (y = 0.074x + 0.40, r = 0.82, P < 0.001). Birds suffered higher mortality than usual in years when snowstorms occurred in the days following their arrival, so that breeding densities in these years were reduced. From Holland and Yalden (1991).

Figure 28.1 Relationship between annual survival of Common Sandpipers Actitis hypoleucos and mean temperature in the latter half of April, soon after arrival in breeding areas, England, 1977-1989 (y = 0.074x + 0.40, r = 0.82, P < 0.001). Birds suffered higher mortality than usual in years when snowstorms occurred in the days following their arrival, so that breeding densities in these years were reduced. From Holland and Yalden (1991).

habitation, where food of some sort was available (for Scarlet Tanager Piranga olivacea see Manville 1957, Zumeta & Holmes 1978, for Oystercatcher see Watson 1980).

Again, little information is available on the impact of occasional heavy spring losses on the overall annual mortality. However, among Common Sandpipers Actitis hypoleucos, which migrate from Africa to breed in Britain, annual survival fluctuated in one area according to the weather in April, when they arrived (Figure 28.1). The mean survival over 13 years was 79%, but following late snowstorms in 1981 and 1989 survival fell to 39% and 50% respectively, and breeding pairs from 21 to 14 and from 20 to 12 (equivalent to 33% and 40% reductions). After both these years, recovery in population level was slow, with annual increments of only 1-2 pairs (Holland & Yalden 1991). Similar reductions in breeding densities in cold springs were estimated for Scarlet Tanager Piranga olivacea at 33% in a study area in New Hampshire (Zumeta & Holmes 1978), at 30% for New Hampshire as a whole, and 50% for Maine; for various hirundines (Tachycineta bicolor, Riparia riparia, Hirundo rustica, H. pyrrhonota) declines were estimated at 30% for Nova Scotia, Maine and New Hampshire, together with an average of 25% in eight species of warblers in New Brunswick, compared to numbers in the previous year (Robbins & Erskine 1975). Hence, all these estimates of local or regional population declines, attributed to cold weather after arrival in breeding areas, fall within the range 25-90%, depending on species and area.

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