BIRDS OF THE CAMBRIDGE REGION. 357 



222. ^A^ilsonia pusilla (Wils.). 

 Wilson's Warbler. Wilson's Bl-^^ckcap. 



Transient visitor, common in spring, uncommon in autunm. 



SEASONAL OCCURRENCE. 



May g, 1895, one male seen, Belmont, W. Brewster. 



May 12 — 25. 

 May 27, 1894, one male seen, Cambridge Region, W. Faxon. 



September 1, 1884, one ad. male taken, Watertown, W. Brewster. 

 September i, 1900, one female or young male seen, Arlington, W. Fa.xon. 



September 5 — 20. 

 November 20, 1S98, one female' taken, Belmont, W. Fa.xon.^ 



A few Wilson's Blackcaps usually appear in our neighborhood as early as the 

 loth or 1 2th of May, but the bulk of the spring flight seldom reaches the Cam- 

 bridge Region before the i6th and sometimes not until the 24th or 25th of the 

 month. At the height of the movement the birds are often common and occa- 

 sionally so numerous that from si.K or eight to ten or a dozen may be noted in 

 the course of a single morning. We meet with them singly, as a rule, perhaps 

 in upland woods (especially among white pines or hemlocks) or even in our city 

 gardens, but oftenest, by far, in dense thickets near water. They occur most 

 regularly and in the greatest numbers in the Fresh Pond Swamps, where they 

 frequent low, bushy willows, and at Rock Meadow, where they are often ob- 

 served among the lower branches of the large white willows that shade the 

 causeway road. Although exceedingly active and restless tliey permit close 

 approach and are easily identified, even when but imperfectly seen, for their 

 motions are not less characteristic than their color and markings. 



During their return migrations, which begin late in August, Wilson's Black- 

 caps are decidedly less numerous — or at least conspicuous — than in spring, 

 and also more given to haunting dry places. Indeed I have seen them oftenest 

 at this season among oaks or pines growing on high ground. Most of them pass 

 southward before the middle of September, but Mr. Ralph Hoffmann has 

 reported- finding a young bird in Belmont as late as November 20 (1898). 



1 No. 48,307, collection of William Brewster. 

 ^ R. Hoffmann, Auk, XVI, 1S99, 196. 



