HAVERSCHMIDT F (1973) Observations on a population of Pied Flycatchers Ficedula hypoleuca. LIMOSA 46 (1): 1-20.

The Pied Flycatcher Ficedula hypoleuca is in Holland a comparatively recent breeding bird. Apart from a few isolated records in the 19th century it nested already in 1910 in the eastern part of the country and sincel about 1940 it increased c'Onsiderably in numbers and it spread continually westward, and it breeds now as far west as the eastern part of the province of Utrecht. Its greatest density is east and north of the river Gelderse IJssel. The breeding population is estimated at about 6000 pairs. The author studied during 1969-1972 by ringing adults and nestlings a populattion in 8 different areas in the neighbouhood of Ommen (Prov. Overijssel 5231 N 06.25 E). (Fig. 2). Pied Flycatchers nest freely in plastic nestboxes (pipes of po1yvinylchloride) (Fig. 1) in deciduollls- and mixed woods and in gardens. A great density is reached in monotonous pinewoods where in an area of about 4 ha 36 pairs nested in 1972 (Fig. 4). Pied Flycatchers arrive in spring in the second decade of April (1969' on 21 April, 1970 on 20 April, 1971 in 15 April and 1972 on 10 April). Males arrive first. In Table 1 the total number of captured and ringed birds is listed, in Table 2 the growth of the population compared with that of tits and in Table 3 the growth of the population in 3 different areas from the first year that boxes were available. Egg laying starts in the last decade of April (1971 first egg on 29 April, in 1972 on 30 April). Figs. 5 and 6 give! a picure of the dates of the first eggs in 1971 resp. 1972 and Figures 7 and 8 of the first eggs of females with known age. Older females seem to start a little earlier than one year old females, the mean date for older females be1ing 8.7 May and of yearling females 10.8 May. The mean clutch size (Table 4) of 555 clutches is 6.19. The clutch size of one-year old females (Table 5) is not smaller than that of older females. The number of first year females in the population (Table 6) decreased constantly from 1970 (72%) till 1972 (25%), apparently because older birds arrive first so that the yearlings find no place and have to move elsewhere. The same was observed with the males though a much smalleT numbeT was captured (Table 7). Second broods were ne,ver established but repeat clutches, several times, at a distance of 20 metres till about 1 Km from the first brood and with a smaller number of eggs. The colour of the upperparts, of the males with reference to the 7 colourtypes established by Drost (1936) was studied in 1971 and 1972 and data are available of 77 males caught when feeding nestlings. 33 (43%) had brownish grey upperparts without a trace of black (Type VII of Drost), 26 (33%) brownish with a few dark markings (Type VI) and 17 (22%) brownish with more dark markings (type V) while only a single male of type II (black upperparts with a brown rump) was established. The colourtype of the males is independent of their age. The hatching success of the eggs is listed in Table 8. Of 1999 eggs 1694 (85%) hatched. Of the fledging success data are only available for 1971. Of 965 nestlings ringed 916 (95%) left the nest. Of 104 females ringed as nestlings. 24 (23 %) nested in later years on their birthplace, while 45 (43%) shifted to other parts within the study area and 25 (34%) settled down elsewhere at a distance of more than 10 Km. Of these 104 females 62 were one year old, 13 (21 %) were breeding on their birthplace, 24 (39%) were nesting in an other part of the study area and 25 (40%) had moved elsewheTe at more than 10 Km distance. Of 47 females ringed as breeding, birds 33 (70%) nested in subsequent years in the place and 4 (9%) nested in later years at distances varying from 22-32 Km. Of 24 males ringed as nestlings 5 (21 %) nested in later years in their place of birth, 16 (67%) moved to another part within the area in which the study took place, whereas 3 (12%) settled down at a distance of more than 10 Km. Two males ringed as adults returned to their fOTIlleT nesting area. Faithfullness of partners during more than one year could not be established. A male that nested in 1971 and 1972 in the same area had another partner in 1972. Its mate of 1971 bred in 1972 with another male in a different part of the study area. Only once a male was found that fed nestlings in two different boxes. Bigamy probably regularly occurs but this could not be established because males could only be captured at a much smaller scale than females. European Pied Flycatcher Ficedula hypoleuca

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