^° 1 1909' VI ] Roberts, Colony of Yellow-headed Blackbirds. 379 



determine what animal or animals it was that devoured these eggs 

 and birds. Presumably some small carnivorous mammal that 

 mounted the reed stalks from the water below, too nimble footed 

 and light bodied to leave any traces of its presence beyond the 

 despoiling of the contents of the nest. A pair of Least Bitterns 

 established themselves in the midst of the Yellow-head colony, 

 building their nest and laying their eggs, and from the unceasing 

 animosity displayed toward them by the Blackbirds, suspicion fell 

 on these birds. One of them was shot and its stomach examined 

 but it contained no traces of eggs or young birds. The dismember- 

 ment of the nestlings would also seem to exonerate the Bitterns for 

 they would certainly have swallowed them whole. The mystery 

 remained unsolved and I leave it for the speculation of those who 

 may be interested. It is but another of those tragedies constantly 

 occurring which seem to show how natural agencies operate to 

 destroy in great numbers birds and other animals, the too great 

 increase of which would seriously disturb the natural balance of 

 things. 



TRANSCRIPT OF NOTES MADE DURING A DETAILED STUDY 

 OF A BREEDING COLONY OF YELLOW-HEADED BLACK- 

 BIRDS NEAR MINNEAPOLIS, MINN., IN 1901. 



Nest I. May 13th. Completed, including lining; entirely dry. 14th. 

 Empty; pair keep close by. 15th to 17th inclusive. Empty. 18th. One 

 egg. 19th. Two eggs. 20th. Three eggs. 21st. Four eggs. 22nd to 

 30th inclusive. Four eggs. 31st. One young bird and three eggs. June 

 1st. Two young birds and two eggs. 2d. Three young birds and one 

 egg. 3d. Four young birds. 4th. Four young birds, pin-feathers 

 showing plainly on two of them. 5th. Four young birds. 6th. Not 

 visited, severe wind-storm. 7th. Nest blown loose and fallen partly 

 over; one young bird dead in water below nest; other three have pin- 

 feathers one inch long. 8th. Empty; all three young birds gone, and 

 also the one that was drowned under the nest yesterday. 



Nest II. May 13th. Just begun; a few strands; no shape or outline. 

 14th. Only one or two additional pieces added — these still wet. 15th. 

 First attempt abandoned and have begun new nest since yesterday eight 

 inches above beginnings of first one. A loosely constructed affair of finer 

 and dryer material than usual; about one-half of walls built; a few broad 

 leaves already in place but nest frail and not at all firmly placed. 16th. 

 Not visited. 17th. Much larger and firmer; now a bulky nest; upper 

 two inches and inside just added, very wet; two strips of broad dry lining 



