WINDEN J VAN DER (2002) Black Tern Chlidonias niger starts primary moult in breeding areas. LIMOSA 75 (1): 34-36.

So far, Black Terns were known to start primary moult directly after the breeding season in postnuptial moulting areas. However, in Dutch breeding areas adults with active wing moult were observed in the period July-August. Observations referred to sightings of birds with gaps in their wings as well as captures ol Black Terns in active primary moult. Ol six birds captured in July, three showed active moult of the lirst one or two primaries and all six were in active tail moult. Mainly birds with replacement or late clutches were moulting primaries. An early start and slow progress of primary moult (and thus small wing gap) might be an advantage for a species depending on flight most of the time, compared to a faster moult process with consequently larger wing gaps. The disadvantage is higher energetic costs in the breeding areas and, especially lor East-European birds il they start moulting during their breeding season to a, migration flight with incomplete wings to postnuptial moulting areasBlack Tern Chlidonias niger

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