Fun to see. Because ducks don’t feed their chicks, it costs a mother nothing to take on the young of other females. And, the probability of a predator taking one of her young from the crèche goes down.
Kevin From: bounce-61078452-3493...@list.cornell.edu [mailto:bounce-61078452-3493...@list.cornell.edu] On Behalf Of Donna Scott Sent: Wednesday, June 20, 2012 8:34 PM To: CAYUGABIRDS-L Subject: [cayugabirds-l] Merganzer w/ 30 ducklings Today, a female COMMON MERGANZER swam by my beach on Lansing Station Rd, Lansing, with 30 ducklings! The ducklings were fairly large, about 2/3 the size of the mother, but still with downy feathers and "baby markings". The mother was leading them all to various shallow areas along the shore and they were all diving and fishing. When one would surface with a small fish in its mouth, some of the others would chase after it trying to get the fish away from the lucky fisher. They ran across the water. Wondering how these Merganzers end up with so many ducklings in tow, I checked Birds of North America (BNA) for more info. This is not the first time I have seen a female with many babies, but this was the most I ever saw! Info in BNA defines the large number of ducklings I saw as "Brood Amalgamation". From BNA: Brood Parasitism Identity Of The Parasitic Species Both intraspecific parasitism (also called egg-dumping) and interspecific parasitism occur in natural cavities and artificial nest sites. In North America, Common Mergansers parasitize and may be parasitized by Common Goldeneye and Hooded Merganser (Zicus and Hennes 1988<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib186>, MLM). Parasitism with Buffleheads and Wood Ducks not reported. Frequency Of Occurrence Occurs frequently in both North American and European populations, particularly where nest boxes are available (Bellrose 1980<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib012>, Eriksson and Niittylä 1985<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib042>). Frequencies are difficult to determine since eggs of conspecifics are similar; different criteria may provide variable estimates. Eriksson and Niittylä (1985<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib042>) considered any nests with ≥14 eggs as parasitized; using this criterion, about 20% of the nests in their study area in Finland were parasitized by conspecifics (likely an underestimate). Maximum reported clutch size (parasitized nests) was 19 in 75 Ontario clutches (Peck and James 1983<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib136>) and 18 in Finland (Eriksson and Niittylä 1985<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib042>). Timing Of Laying In Relation To Host’s Laying Early nests tend to be more parasitized than late nests (MLM). No information of daily egg-laying times. Response To Parasitic Mother, Eggs, Or Nestlings Host females do not defend their nests against parasites; antiparasite defenses probably consist primarily of nest desertion when clutch sizes are large, as in other members of the waterfowl tribe Mergini. In nest, host female incubates parasitic eggs. Effects Of Parasitism On Host No deleterious effects reported. Success Of Parasite With This Host Absence of reports of parasitic egg recognition and rejection or common clutch desertion suggests parasitism is a successful strategy, although conclusive studies lacking. Brood Amalgamation (Creche Formation) Mixed broods of >40 young observed in ne. Ontario (MLM). Although this behavior is well-known for Common Mergansers, few definitive studies (Eadie et al. 1988<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib041>). Amalgamation not common when ducklings <7 d old, but occurs frequently after that (Dement’ev et al. 1952<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib038>, Palmer 1976<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib135>). Some authors suggest aggressive females “kidnap” young from less aggressive females (Speirs 1985<http://bna.birds.cornell.edu/bna/species/442/articles/species/442/biblio/bib162>); no study has documented this, and it may simply represent confused young joining incorrect mother (A. Erskine pers. comm.). --Donna Scott Donna L. Scott 535 Lansing Station Road Lansing, NY 14882 d...@cornell.edu<mailto:d...@cornell.edu> -- Cayugabirds-L List Info: Welcome and Basics<http://www.northeastbirding.com/CayugabirdsWELCOME> Rules and Information<http://www.northeastbirding.com/CayugabirdsRULES> Subscribe, Configuration and Leave<http://www.northeastbirding.com/CayugabirdsSubscribeConfigurationLeave.htm> Archives: The Mail Archive<http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html> Surfbirds<http://www.surfbirds.com/birdingmail/Group/Cayugabirds> BirdingOnThe.Net<http://birdingonthe.net/mailinglists/CAYU.html> Please submit your observations to eBird<http://ebird.org/content/ebird/>! -- -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
