female ducks negotiate joint rearing of ducklings

To: Birding Aus <>
Subject: female ducks negotiate joint rearing of ducklings
From: L&L Knight <>
Date: Sat, 13 Jan 2007 11:50:11 +1000

Public release date: 10-Jan-2007
It takes a village -- female ducks negotiate joint rearing of ducklings

Waterfowl are "careful, sophisticated bargainers," negotiating not only how much effort each puts into communal rearing of ducklings, but also profit-sharing, says a new study from the American Naturalist.
Click here for more information.

Female eider ducks are well known to team up and share the work of
rearing ducklings, but it now appears that they also negotiate not only how much effort each puts into the partnership, but also
profit-sharing. An international group of scientists used a
long-running study of the eider population in a Finnish archipelago to test predictions about how each hen seeks to maximize her benefits from the partnership without making it so unattractive that other hens
withdraw their participation.

As hens arrive at the rearing-area with their ducklings, a period of
intense socializing ensues. The hens then sort themselves into cliques – pairs, trios, or quartets – with each hen in a group assuming a
distinct role.

"Waterfowl have a reputation as being none-too-bright, but we think
they are careful, sophisticated bargainers," says team leader Markus
Öst (University of Helsinki). "The socializing during the period prior to group formation is devoted to the searching for and negotiating with a suitable partner."

As a group, each hen's ducklings are kept warm, led to food, and
fiercely defended against predatory gulls – all tasks for which central
positions in the brood are the best and safest. Though the ducklings
appear identical to human observers, hens can clearly recognize them
and carefully manage their ducklings' locations in the joint brood,
apparently according to an agreement worked out with the other hens.

Behavioral ecologists have long been interested in so-called
'co-operative breeders,' but ducks have never before been considered in this category. Appearing in the January issue of The American
Naturalist, this study expands the range of animal groups considered
co-operative breeders and also suggests that the behavioral strategies involved may be more complex than previously thought.

Öst, Markus, Colin W. Clark, Mikael Kilpi, and Ron Ydenberg, "Parental effort and reproductive skew in coalitions of brood-rearing female
common eiders." The American Naturalist: January 2007.

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