PRIMARY RESEARCH PAPER Hatching in dabbling ducks and emergence in chironomids: a case of predator–prey synchrony? Lisa Dessborn • Johan Elmberg • Petri Nummi • Hannu Po ¨ysa ¨ • Kjell Sjo ¨berg Received: 27 April 2009 / Revised: 7 September 2009 / Accepted: 5 October 2009 / Published online: 23 October 2009 Ó Springer Science+Business Media B.V. 2009 Abstract It has been hypothesized that dabbling ducks (Anas spp.) time breeding to coincide with annual regional peaks in emerging dipterans, espe- cially Chironomidae, which are important prey for newly hatched ducklings. However, this hypothesis has never been evaluated in a replicated lake-level study, including year effects in emergence patterns. We collected duck and invertebrate data from 12 lakes during the nesting seasons 1989–1994 in a watershed in southern Finland. The oligotrophic study lakes are typical of the boreal Holarctic, as are the three focal duck species: mallard Anas platyrhynchos L., widgeon Anas penelope L and teal Anas crecca L. Hatching of ducklings showed a clear peak in relation to ambient phenology (annual ice-out date of lakes), whereas chironomid emergence was more erratic and showed no clear peak at the lake level, although total watershed-level emergence was somewhat higher before and long after the duck hatching peak. Thus, we find no evidence that ducklings hatch in synchrony with abundance peaks of emerging chironomids. There was large within- year temporal variation in chironomid emergence among lakes, but this was not correlated with ambient temperature. The rank of individual lakes with respect to the abundance of emerging chironomids was consistent among as well as within years, a predictability that ought to make adaptive lake choice by ducks possible. On the lake level, there was a positive correlation between the total amount of emerging chironomids and brood use. We argue that emergence patterns of chironomids on typical boreal lakes are neither compressed nor predictable enough to be a major selective force on the timing of egg- laying and hatching in dabbling ducks. Despite spatial (among-lake) patterns of abundance of emerg- ing chironomids being predictable within and among years, the observed pattern of brood use suggests that other factors, e.g. habitat structure, also affect lake choice. Keywords Teal Á Mallard Á Widgeon Á Reproductive timing Á Food peak Handling editor: Stuart Anthony Halse L. Dessborn (&) Á J. Elmberg Aquatic Biology and Chemistry, Kristianstad University, 291 88 Kristianstad, Sweden e-mail: lisa.dessborn@hkr.se L. Dessborn Á K. Sjo ¨berg Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, 901 83 Umea ˚, Sweden P. Nummi Department of Forest Ecology, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland H. Po ¨ysa ¨ Finnish Game and Fisheries Research Institute, Joensuu Game and Fisheries Research, Yliopistokatu 6, 80100 Joensuu, Finland 123 Hydrobiologia (2009) 636:319–329 DOI 10.1007/s10750-009-9962-y