EPOW - Ecology Picture of the Week

Cormorants in a Row

Double-crested Cormorant (Nannopterum auritum [prev. Phalacrocorax auritus]), Family Phaacrocoracidae
Chesapeake Bay, Maryland, USA

Explanation:  Got your cormorants in a row?  On a work visit to Chesapeake Bay, Maryland, we spotted these common denizens of the wetlands.  Here, these Double-crested Cormorants occur during the summer and move to the southeast U.S. for wintering.  

But it's not that simple.

A related species, the Crested Cormorant (Gulosus aristotelis), has been changing its migration pattern in the face of climate change.  Like the Double-crested Cormorant, the Crested Cormorant is partially migratory, with some individuals migrating along coastlines and other remaining year-round resident.  In recent field studies, the Crested Cormorant recently been migrating in greater numbers in response to increases in more extreme winter events and storms.  Somehow, the birds detect the impending arrival of such events, but whether this is a learned behavior or is also passed on genetically is as yet undetermined.  Further, studies of other cormorant species are also revealing behavioral migratory changes in response to changes in weather and climate patterns.  

And if Double-crested Cormorants that use migratory flyways are also changing their migration patterns is also yet to be determined.  

Information:
    Aðalsteinsson, S., A. López, and T. Bregnballe.  2023.  Timing of spring migration of Norwegian Cormorants Phalacrocorax carbo: long-term trends and effects of winter severity.  Seabird 35:41-57.
    Bregnballe, T., C. Herrmann, K.T. Pedersen, J. Wendt, J. Kralj, and M. Frederiksen.  2022.  Long-Term Changes in Winter Distribution of Danish-Ringed Great Cormorants.  Ardea 109(3):327-340.
    Kimble, S.J.A., B.S. Dorr, K.C. Hanson-Dorr, O.E. Rhodes, Jr., and T.L. Devault.  2020.  Migratory Flyways May Affect Population Structure in Double-Crested Cormorants.  Journal of Wildlife Management 84(5):948-956.