technique called "gaping"). Orians also ex-

plains how food and habitat have affected

blackbirds' social relations and other be-

havior. The book concludes with a thoughtful

essay on the relationships between people and

blackbirds, providing special insight on each.

Blackbirds of the Americas treads the line

between popular writing and science. A few

tables and figures dot the text and selected

references follow. Though well-written, the

book is full of information and may be slow

reading . Tony Angell's careful drawings , il-

lustrating the species and their behavior, add

to the appeal of the book. By reading this

book, someone whose interest in birds goes

beyond simple identification can learn a lot

about ecology and evolution as well as about

blackbirds. The result will be more satisfac-

tion in birdwatching .

I appreciate the comments of Taber Allison

and Billy Goodman to improve this review .

-David E. Blockstein, Bell Museum of

Natural History, Dept. of Ecology and Be-

havioral Biology, University of Minnesota,

Minneapolis, MN 55455.

Foot Tumor Found on Juvenile Common Loon

*Ross H. Hier•, Pamela Skoog Perry2, and Mark Sperry•

Tumors are extremely rare in free-flying

wild birds even though they are not uncom-

mon in domestic birds (Sanger 1971, Sieg-

fried 1983) . Hard, nodular masses may often

be observed on the palmar and lateral aspects

of the avian foot but these are considered

fibromas or fibromatous corns and not true

tumors (Fox 1923). In a search of the litera-

ture, a necrotic tumor mass on the foot of a

mature ruffed grouse was described by Sieg-

fried ( 1983) but reports of similar tumors on

loons or other waterbirds were not found.

During August 1982, a juvenile Common

Loon (Cavia immer) was observed by

lakeshore residents on Upper Gull Lake in

Cass County , Minnesota, that seemed to have

a fishing line and bobber entangled around

one of its feet. Concern for the bird resulted

in its capture on August 19 by Minnesota

Department of Natural Resources personnel

using a night-lighting technique (Lindmeir

and Jessen 1961).

The loon's swimming efficiency was

greatly impaired; therefore capture was rela-

tively easy for a loon of this age-class. The

bird appeared to be underweight as evidenced

by a protruding keel. Plumage was charac-

teristic for a fully feathered but flightless

Common Loon (i.e., "dappled gray" sides

and back) except for the retention of down

on much of the nape. This condition differs

from plumages of other loons of similar age-

class (n = 15) handled during banding by Hier

Spring 1986

and Sperry, and may indicate that the bird

was suffering from a nutritional deficiency.

Upon having the bird in hand it was appar-

ent that the loon was not dragging a fishline

41