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The Mystery of the Black—billed Cuckoo

BY GERALD H. THAYER

NCREDULITY will doubtless be the predominant note in the reception of the strange tale which I am about to unfold, yet living evidence of its truth is yearly accessible to any one who has leisure

and inclination to seek it. I refer to the mid-summer, mid-night. mid- sky gytations of the Blackebilled Cuckoo. as noted by my father and me for three consecutive seasons in the southwestern Corner of New Hamp- shire. Here, in the country immediately surrounding Mt. Monadnock, the Blackebilled Cuckoo is a fairly common summer resident, while the Yellow-billed occurs only as a rare autumn migrant.

Several years before we discovered the nocturnal-flight phenomenon, we began to be puzzled by the extreme frequenty of Cuckoo calls on summer nights, These calls were far commoner than the same bird‘s daytime noises; in fact, a week might pass without our seeing or hearing any Cuckoos during the daylight hours, while they were nightly vociferous around the house. They uttered both the (Murrow notes and the rolling guttural call; but the gurtural was much the commoner of the two, except on dark, foggy nights, when the caSe was usually reversed. The explanation of this diﬁerence was not immediately forthcoming, but was suggested a summer or two later by our discovery that the birds were almost invariably seated when they made the [aw-raw note, and always in ﬂight when they made the rolling guttural.

From this time onward I spent many evenings out-of—doors, 0n the roads and in the woods and ﬁelds. I also slept out, on uncovered piazzas, in an open tent, and occasionally on mothereearth on a high peak of NIL Monadnock, These evenings and wakeful minutes of the nights gave me unique opportunities to study nocturnal bird-notes, and I had many interesting experiences. Chief among these was the discovery, incredible at ﬁrst, but gradually forced upon my belief by steady accretion of the