16 TAVERNER, Birds of Red Deer River, Aha. 



[Auk 



[Jan. 



identity of many of these birds and many may have been Swainson's 

 instead of Red-tails. In all twenty- two specimens were taken. Of these, 

 except for a very faint to pronounced barring of the tail, there is no constant 

 character to separate them from eastern borealis. They average slightly 

 darker on the under-parts but at least two birds are lighter here than typical 

 eastern birds while several are indistinguishable in this respect. Many of 

 the tails are very light, but new incoming plumage of richer coloration 

 indicates that this is due to the bleaching power of the bright prairie sun 

 and is an acquired and not an inherent character. Fading however does not 

 account for all the lightness, as in some cases the feathers are mottled 

 or suffused with white from the shaft outward. While this culminates 

 in a female taken July 9, the half grown offspring of the same bird has a 

 dark tail similar to eastern juveniles, while all other juveniles having 

 enough tail to judge from, show appreciable amounts of intermixed red 

 such as is not seen in eastern birds. 



I was in hopes that we would find krideri occupying this desert-like 

 country but was disappointed, as we procured nothing that could not be 

 attributed to calurus. One interesting point observed was that like 

 usually mated with like, a light bird generally had a similarly colored 

 mate and vice versa. Only in one case did we definitely discover a very 

 dark bird paired with a light one. We obtained the three young of this 

 pair and while they are hardly sufficiently fledged to accurately determine 

 the characters they would finally exhibit, they show considerable difference 

 in color. One tends towards an almost uniformly dark bird while the 

 other two have plain indications of cream colored breasts and throats. It is 

 evident therefore that the darkness of plumage is a congenital condition 

 and not assumed with age; also that there is often a large amount of red 

 in the tails of many juvenile birds such as is never (?) shown in eastern 

 specimens of comparable age. 



Naturally the abdomens of all the adults taken in the midst of the breed- 

 ing season were bare; the skin was thickened and rugose, covered with 

 dry, horny, scab-like plates that peeled off while skinning, and now that 

 incubation was over, seemed ready to shed naturally before the incoming 

 down of the midsummer moult. In addition to this, however, the throats 

 were similarly affected. The throat feathers were ragged, worn and thin, 

 whilst the skin between was excessively warty, the prominences tending to 

 clear yellow in color and similar in appearance to the wattles of gallinaceous 

 birds. It suggests that the throat is used in incubation as well as the 

 abdomen. 



The value of these large Buteos to the farmers of the prairie provinces 

 is incalculable. This applies equally to Swainson's Hawk and the Ferrugi- 

 nous Roughleg. The country is infested with gophers, mostly Richard- 

 son's Spermophile in the section we visited, but Franklin's and the 13 -lined 

 were also present. Upon these the large hawks seem to feed almost entirely 

 and their great number must be a powerful check upon them. However, 



I 



