HAGEMEIJER W (1994) Invasie van Roodpootvalk Falco vespertinus in het voorjaar van 1992: grootste invasie van deze soort in Nederland. LIMOSA 67 (1): 7-14.

In The Netherlands the Red-footed Falcon is a regular visitor, generally in small numbers, since the end of the 1960s. In the spring of 1992 a large influx took place; it is documented here mainly by using observations gathered by SOVON (Rare Non-breeding Species Project) and the Dutch Birding Association (telephone line). The influx of 1992 started in mid-May and peak numbers were counted around 14, 22-24 and 30-31 May (maximum on 30 May, 160 birds). In early June some tens of birds were recorded, but by mid-June numbers had dropped markedly (fig. 1). In July-October only a few birds were recorded. Relatively many birds were recorded in coastal areas (fig. 2). In the first two decades of May most birds were recorded in the SW of the country, whereas in the last decade of May largest numbers were observed in the N and NE. Prior to 25-31 May, most birds observed were actively migrating, but staging birds dominated later on. Relatively many inland observations were made in heathland areas and peat moors. Of all birds sexed (N=444) 48% was in male plumage. In the first weeks of the influx males were relatively more numerous than later on (8-20 May 61%, 21-31 May 44%, difference statistically significant). Adult birds formed a minority (36%, N=223), especially among males (23%, versus 51% in females). Adult birds were mainly recorded during the first weeks of the influx (1-20 May 67%, from 20 May on 33%) (fig. 3). The total number of Red-footed Falcons involved in the 1992 influx is estimated at 1500-2000, based on a number (after correction for double counts) of at least 1111 birds observed. The influx of Red-footed Falcons in 1992 coincided with unusually large numbers of migrating Honey Buzzards, Montagus Harriers, White and Black Storks, Bee-eaters, Red-throated Pipits and Scarlet Rosefinches. It is likely that their occurrence has been favored by the strong and persistent easterlies in May-June. Large numbers of Red-footed Falcons were equally recorded in Belgium, England and Skagen, Denmark (fig. 4), but not in Sweden. Compared to previous influxes of Red-footed Falcons in The Netherlands, the 1992 influx was by far the largest, although this may be somewhat exaggerated as the number of observers, their technical equipment and their skills in identifying difficult species has increased considerably in recent decades. Fig. 5 shows the numbers recorded in The Netherlands in 1988-92, when observations were systematically recorded by SOVON.

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