The Zoologist/4th series, vol 6 (1902)/Issue 730/On Mr. Selous' Theory of the Origin of Nests, Howard

by Henry Eliot Howard

 

ON MR. SELOUS' THEORY OF THE ORIGIN OF
NESTS.

By H.E. Howard, F.Z.S.

 

In his article on the Great Crested Grebe in this Journal (1901, p. 339), Mr. Selous made reference to "one of two rival Wheatears catching up a piece of grass in the midst of violently excited movements," adding that he would recur to the explanation of this habit. I therefore looked forward with much interest to his explanation of a habit which I admit had puzzled me for some years, and which, taking his observations in conjunction with my own, I now feel sure is probably—if we only knew it—to be found amongst the majority of species. I therefore think it best to put my own observations on record, as they appear to me to very much strengthen the foundation on which his theory of the origin of nests is built—a theory which, to my mind, now that I look back upon the same, to me, unintelligible sexual movements which I have from time to time observed, appears to be placed outside the category of a provisional hypothesis.

In an article on the Grasshopper-Warbler (Zool. 1901, p. 61), I described the male of this species picking up a dead leaf, and following the female with it in his bill, while mating. But this only very tamely describes what really happens, and if it had not been for Mr. Selous I should still have been satisfied with the conclusion I then arrived at, viz. that it was an outward sign of the one absorbing picture in the bird's mind—the construction of its nest. Sexual frenzy precisely describes the condition of the males of the above species at this time—that is to say, during the week or so they are mating—and in every case where I have closely followed their movements at this period, they have performed the same curious ceremony, usually in the midst of intensely excited and nervous actions. These movements are characterized, as a rule, in the following way: The male walks—you might almost say struts—along in front of the female, picks up a leaf, again walks on for a little, drops it, and disappears with quick darting flight after another—probably rival—male. Presently he returns, crawls to the top of a bush, commences to sing, in the middle suddenly breaks off, and again darts off after the other male, then returns and marches on in front of the female, and again picks up and carries a leaf. She meanwhile threads her way in and out of the dead and growing herbage, apparently unconscious to anything that might in any way tend to produce the same nervous tension in her own mind, and oblivious to the sexual selection proceeding around her. In fact, I cannot call to mind a single case where I have seen anything approaching frenzy in the female of any species while mating.

The conclusion I formed after remarking the behaviour of the males at this season was that the picking up and carrying of a leaf was due solely to the fact that, inasmuch as the construction of the nest must be commenced within a few days of the time of my observations, and the bird's mind being full also of this same idea, this action might be ipso facto a commencement; but, in the light of later observations, any theory of this kind falls to the ground. The following spring I was attracted by the movements of a Blackcap flying from tree to tree in hurried flight, carrying a piece of one of the dead grasses with which the nest is generally constructed. But herein lies the difference—that it was one of the first Blackcaps that had arrived, and there was no sign of any female; in fact, the females had not arrived. Again, last year, the first Whitethroat arrived in this district—and how well I remember the day—on the 20th April, the first day of that long spell of dry weather. The sun was just rising, and the rays of light coming through a slight mist gave all the trees and foliage that extraordinary glow which those who are accustomed to being out at that time of day will readily understand. Not having seen the bird for six or seven months, I thought I must sit down and watch. The bird was in that state of restless frenzy, at one moment diving into a bramble-bush, then climbing up the topmost sprays, singing all the while intermittently. After one rather longer dive into the bush than usual, he reappeared, carrying a piece of dead grass in his bill, full of excitement, flying from spray to spray, with no apparent object for so doing. Again, as in the case of the Blackcap, no female was present, the females, as we all know, arriving late.

One more case—this time a Hedge-Sparrow. The male was hopping along a wall in front of the female, carrying a piece of straw, excited, as far as Hedge-Sparrows can be, shuffling his wings and flirting his tail. But, as Mr. Selous aptly remarks, it is the beginning of everything that is fraught with such significance. Is this a non-purposive movement springing out of sexual passion, or is it an outward representation of an idea contained in the bird's mind?

It appears to me that the fact of the male Blackcap and Whitethroat going through this performance before any females had arrived tends to prove that it belongs to the former hypothesis rather than to the latter, and thereby upholds Mr. Selous' theory that this was the origin of the nest. For, watch a Blackcap on his arrival, or any other male before actually having mated, and you will see that his or their movements point to the fact that all the thoughts are concentrated on the one object—the possession of a female—and to attain this object all their powers, chiefly vocal, are directed. Any thought of the construction of a nest—if really there is at all at this period, which I am inclined to doubt—must be in comparison with the other momentous event in the bird's life wholly insignificant. At no time are the vocal powers of the Blackcap shown to such an advantage as when mating; his song then is continuous. When not loud it is a low expressive warbling, and if you will watch him you will see that his whole body is trembling with this nervous excitement. At this time also he puts himself in all kinds of curious contortions. I have seen him carry his tail more than at right angles to his body, which he does at no other period of his life. The same thing may also be said of the Whitethroat, only, in his case, warbling would hardly express his nervous vocal production—it is more of an angry scolding.

Again, the Chiffchaff only floats about the air like a big moth when trying to win a mate. Much the same might be said about the Garden Warbler.

The Marsh-Warbler produces far more vocal variations at this time. The Red-backed Shrike never mimics to such perfection as when mating. I have heard in succession Swallow, Partridge, and Starling most perfectly imitated. And at what other time does he go through those extraordinary, what one might call, gestures to the female; he does all he can to speak? At times, when he twists his neck round and turns his head upward, he appears to be imploring heaven to help him.

I could mention many similar cases, but these, I think, are sufficient to prove that the whole powers of the bird's body and mind are concentrated solely on the possession of a female. This being so, it appears to me to be highly improbable that this action can in any way refer directly to the construction of the nest.

For a minute let us consider it simply expressive in practical form of a mind overburdened with the mental image of a nest and all that pertains to its construction, and that it is in no way associated with any sexual passion. Assuming this, then, why do we not find the same action in the female? Assuredly to her the nest must mean as much, if not more, than to the male; and if this was only an expression of delight on the part of the male at the return of the breeding season, it is only reasonable to suppose that we should find the same or some similar action in the female. But the fact is clear to my mind that in no case have I found any similar action in the female. I admit my observations are few, and can in no way be thought of as anything in the nature of proof; but, taken in conjunction with Mr. Selous' own observations, I think it will be admitted there is reasonable basis upon which his theory is raised.