232 



Genus Sialia. Bluebirds. 



766. Bluebird. FR. LE ROUGE-GORGE BLEU. Sialia sialis. L, 7-01. Plate L B. 



Distinctions. The only solidly blue bird with a reddish breast among Canadian 

 species the Indigo bird is blue but lacks the red breast. Females and juveniles are duller 

 in colour and the breasts of young birds are spotted with brown but all have the character- 

 istic blue backs. 



Field Marks. The bright blue coloration of the back and the earthy red of the 

 breast. 



Nesting. In hollow trees, posts, or stubs or in bird houses, in nest of grasses. 



Distribution. Eastern North America, west to the prairie provinces and north nearly 

 to the bounds of settlement. 



SUBSPECIES. The subspecies of Bluebird occurring in Canada is the typical 

 race, the Eastern Bluebird. 



The Bluebird arrives in the early spring with the Robin and the 

 Meadowlark. It is a confiding bird building in the hollows of old apple 

 trees, holes in fence-posts, bird boxes, or nests abandoned by Wood- 

 peckers. It is characteristically a bird of the orchard and with a little 

 encouragement will build in bird houses in the garden where its gentle 

 ways, pretty murmuring notes, and brilliant coloration make it quite 

 an acquisition. 



Economic Status. The Bluebird feeds mainly upon insects and is, 

 therefore, highly beneficial. Weed seeds form an important part of its 

 food and it eats some soft fruit, but practically no cultivated kinds are 

 taken. Hence the Bluebird can be regarded as a consistently useful bird. 



GLOSSARY. 



Albinism. The occasional and erratic occurrence of white specimens, either pure or 

 partial, complete or in irregular spots, in species that normally are not white. It is nothing 

 more than a freak caused by a deficiency of colouring matter in the plumage (See p. 6). 



Axillars or Axillaries. A fan-shaped group of feathers under the wing closing the 

 space between the innermost flight feathers and the body when in flight. 



Bars. In descriptions of bird coloration, bars designate lines across the body and not 

 parallel with the shafts of the feathers (See stripes). 



Cere. A wax-like swelling about the base of the upper mandible, present in some 

 species, especially the Hawks. See Figure 33a and b, p. 23. 



Coverts. The feathers covering the bases of the larger flight and tail feathers. There 

 are upper and underwing-coverts and upper and under tail-coverts. The upperwing- 

 coverts are divided into greater and lesser coverts, the former being the largest line imme- 

 diately next to the flight shafts and resembling them to some degree in texture (Figure 1 

 p. 18). 



Crepuscular. Pertaining to twilight. 



Crown. The top of the head from the forehead to near the base of the skull. 



Culmen. This may be called the ridge line of the bill. Viewed sideways, the line 

 forming the top outline of the bill from the spring of the first forehead feathers to the tip is 

 the culmen line. It is measured in a straight line, as with dividers, not following the curves 

 as with a tape line (Figure 1, p. 18). 



Dichromatism. The normal occurrence of two different colorations in the same 

 species due to neither sex, season, nor age and only partly hereditary. Both colorations 

 may occur in the same brood though the tendency is for like to produce like and one form 

 may predominate in any given locality (See p. 6). 



