shallow waters from 1 1/2 to 6 ft deep. Palmer (1976b) added that Common Mer- 

 gansers regularly feed in deep or shallow rapids. Most foraging occurs in clear 

 water, because Common Mergansers visually select and follow their prey; most 

 food is taken near the bottom (Palmer 1976b). 



Winter and Offshore Dement' ev and Gladkov (1952) stated that the most char- 

 acteristic winter habitat was the mouths and pre-estuarine regions of rivers. 

 Cramp et al. (1977) indicated that any large body of open water is used, and 

 use of marine waters is only incidental. These authors remarked that Common 

 Mergansers can only be regarded as sea-ducks to a minor degree because they seek 

 out fresh water and may winter inland on almost any large reservoir, lake, or 

 river. Bellrose (1976) indicated that the increase in wintering populations in 

 states such as Oklahoma and Kansas was probably the result of the building of 

 many reservoirs and impoundments. Palmer (1976b) indicated that Common Mergan- 

 sers are a shoalwater species and thus are usually found near the shore. 



FOOD AND FEEDING BEHAVIOR 



Common Mergansers principally dive from the surface for their food, pro- 

 pelling themselves with their feet as they chase their prey. They swim with 

 their heads submerged and dive in all but shallow water. Occasionally, these 

 mergansers may "tip-up" to seize prey. They also occasionally probe around 

 near stones near the bottom. Food is occasionally stolen from gulls and they 

 have been observed feeding on dead or dying fish that had been caught in tur- 

 bines (authors cited Jji Cramp et al. 1977). 



Most dives are shallow but these ducks have been caught as deep as 35-40 

 ft (11-12 m) in gill nets (Palmer 1976b). Submergence times are usually about 

 30 sec, but may range up to about 2 minutes. They feed most actively in the 

 early morning and evening. The pattern of feeding behavior may vary from area 

 to area (authors cited _in Johnsgard 1975, Palmer 1976b, Cramp et al. 1977). 

 More detailed accounts of feeding techniques and interactions with other spe- 

 cies may be found in Johnsgard (1975), Palmer (1976b), and Cramp et al. (1977). 



Various studies (e.g., Johnsgard 1975, Palmer 1976b) agree that Common Mer- 

 gansers are opportunistic feeders. They feed on whatever is most plentiful and 

 most easily available, primarily fish. Recent summaries (Johnsgard 1975, Bell- 

 rose 1976, Palmer 1976b, Cramp et al. 1977) indicate that as little as 75% of 

 the diet may consist of fish but often all food identified is fish. A great 

 variety of fish are consumed; Palmer (1976b) indicated that this merganser is 

 known to eat at least 50 species of fish. Other food items ingested include 

 fish eggs and fry, frogs ( Rana ) , salamanders ( Ambystoma ) , crustaceans (shrimp, 

 crayfish, crabs), molluscs (mussels, crabs), insects and their larvae, and ner- 

 eid annelids (authors cited above). On rare occasions they have been known to 

 eat birds and they occasionally even eat Water Shrews ( Neomys f odiens ) and water 

 snakes (Cramp et al. 1977). 



The authors cited above provide exhaustive lists of species eaten. Their 

 summaries, as well as the papers cited therein, should be consulted for further 

 details. Hansen (1978c) and Anderson and Reeder (1977) give more recent infor- 

 mation on food habits than that provided by the handbooks; we do not summarize 



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