Het voorkomen van luisvliegen op nestjongen van boombroedende roofvogels in Saarland

This study describes the infestation of raptor chicks with louse flies, based on frequent visits to nests with chicks of Buzzard Buteo buteo (n=79 visits, 1996-98), Sparrowhawk Accipiter nisus (n=30, 1996-98), Goshawk A. gentilis (n=8, 1996-98), European Honey-buzzard Pernis apivorus (n=8, 1996-98), Red Kite Milvus milvus (n=12, 1997-98, 2004) and Black Kite Milvus migrans (n=10, 1997-98, 2004). Nests (not the individual chicks) were coded as infested or not. Each chick was sexed (if possible) and measured (wing length and body mass). In Honey-buzzard (all visits in July) nor Black Kite (late May-mid June) louse flies were recorded. In Red Kite, only 1 out of 12 nests was infested, i.e. none of 10 nests in the 3rd decade of May and 1 of 2 nests in the first decade of June. Few Goshawk nests were infested with louse flies, i.e. none in late May (1 nest), once early June (n=6) and once late June (n=1). Mean number of nestlings was 1.5 in infested nests, and 3.17 in non-infested nests (notice small sample size). Sparrowhawk nests often held louse flies: 4 out of 9 nests in mid-June, 10 of 16 nests in late June, all 4 nests in early July and none in 1 nest in mid-July. Considerable variation in the annual infestation frequency was recorded: 1 out 7 nests in 1996, 10 out of 14 nests in 1997 and 7 out of 9 nests in 1998. The number of nestlings in infested nests averaged 4.06, against 4.25 in non-infested nests (difference not significant). Infested nests had a female-biased sex ratio of 34:40; non-infested nests had a slight preponderance of males (27:24). In the Buzzard, 8 out of 79 nests were found to have louse flies, mostly late in the breeding season: 0/2 nests early May, 0/6 nests mid-May, 0/32 nests late May, 0/24 nests early June, 7/13 nests mid-June, 1/2 nests late June. Infested nests averaged fewer chicks than non-infested nests, i.e. 1.25 and 1.58 respectively. Chicks on infested nests seemed to weigh slightly less than on nests without louse flies (Fig. I).