Female deserts brood, male raises chicks

Friday, May 13th, 2011

Species: European Honey Buzzard

Project: Honey Buzzard habitat use and ranging on breeding and wintering sites

Figure 1: Leaving the breeding territory at 10:00 UMT on 4 August 2009 for a staging area 64 km SSW of the nest.

Male and female Honey Buzzards increasingly show less overlap in home range as the season progresses. In this particular case the female reduced the overlap to zero. She deserted the nest with two chicks of 32 and 35 days old (fledging at 42-45 days), and flew to a staging area some 64 km away. By that time, growth of the younger chick was already retarded. Her male (bird 182) cared for both chicks for another two and a half weeks until independence. In 2010, she repeated this behaviour (but returned twice) when the single chick was only 9 days old. The male remained on duty but at this age the chick still needs to be brooded, an activity hard to combine with foraging for a single parent.


Figure 2: Restricted home range during 18 days prior to migration.

Figure 1 shows female 179 leaving the breeding area in the morning of 4 August 2009, travelling 90 km to reach her intermittent staging site. She took up residence in a dry forest-sand dune area surrounded by agriculture and fragmented broad-leaved humid forest (Figure 2). Her small home range (some 4 sq km) and fixed roost sites resemble wintering behaviour. Based on plumage, the age of chicks differed by ten days, whereas the actual age difference was only 2.5 days (Figure 3), showing the extent of growth retardation in the second chick.

Figure 3. Chicks aged 27.5-30 days, at this moment the growth difference is already equivalent to 7 days. 29 July 2009, five days prior to their mother’s desertion.

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