August, 1912. The Irish Naturalist, 137 



GRASSHOPPER-WARBLERS ON MIGRATION 

 OBSERVED AT THE TUSKAR LIGHTHOUSE. 



WITH SPECIAL REFERENCE TO THE BEHAVIOUR OF THIS 

 SPECIES UNDER THE INFLUENCE OF THE 

 LUMINOUS BEAMS. 



BY PROFESSOR C. J. PATTEN, M.A., M.D., SC.D. 



" Were it not for its crepuscular and skulking habits the 

 bird would be far better known." The words are Mr, 

 Ussher's, and the quoted sentence is taken from his article 

 on the Grasshopper-Warbler in " The Birds of Ireland," 

 pp. 25 and 26. I make the quotation at the outset because 

 I believe that Mr. Ussher has had considerable personal 

 knowledge of this warbler in its natural habitat. My 

 own experience as far as it goes is quite in accord with that 

 of Mr. Ussher. I believe the bird has been greatly over- 

 looked in Ireland. For reasons which shall be put forward 

 presently I hope to show that we have strong presumptive 

 evidence that this warbler arrives in Ireland in considerable 

 numbers during April and early May. It is very remarkable 

 that its skulking habits are actually practised at such an 

 extraordinarily unusual site as is afforded by the frame- 

 work of the lighthouse lantern and moreover under the 

 dazzling influence of the luminous beams. These weird 

 habits no doubt have been the means of screening the bird 

 from the eye of the lightkeeper or even on many occasions 

 from the trained eye of the ornithologist. Very shortly 

 after I had commenced making observations on birds at the 

 lighthouse lantern, I was deeply impressed with the different 

 and at the same time characteristic behaviour of various 

 species as they came under the influence of the luminosity 

 of the rays. It would take us too far afield to consider 

 this subject even in quite a general way in regard to various 

 species ; in this paper I must confine my remarks to the 

 behaviour of the Grasshopper-Warbler under such con- 

 ditions. That the bird was a frequent visitor to the lantern 

 during the zenith of its spring migration is seen from the 

 fact that between April 12th and May 4th I collected four 



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