(170) COURTSHIP AND DISPLAY OF THE SLAVONIAN GREBE.

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1 (170) COURTSHIP AND DISPLAY OF THE SLAVONIAN GREBE. BY ERIC J. HOSKING, F.R.P.S., M.B.O.U. (Plates 4 and 5.) DURING the nesting season of 1939 I was staying in Scotland and had the opportunity of witnessing a unique courtship and display of the Slavonian Grebe (Podiceps auritus). I am indebted for this experience to the Rev. H. M. Stone, of Worcester, who escorted, me to a loch where these Grebes have been known to nest for many years and several nests were found. One was selected giving the best surroundings and position for" photography and a photographic hide was erected some distance away. This was on June 7th, and the nest then contained three eggs which were fresh. On revisiting the site the following day with a view to moving the hide nearer to the nest, we found that one egg was missing. On June 15th there was only one egg remaining in the nest, and, as the Grebes were still incubating this egg and appeared to be quite tame, it was decided to bring the hide within working distance. The reason for the disappearance of two eggs was puzzling, but was eventually attributed to a nearby colony of Black-headed Gulls which were continually foraging round the loch. It was noticed on this day that the egg was not being covered by the parent bird when leaving, and it was found uncovered on subsequent occasions. One of the pair, which when mating occurred proved to be the hen, was in very unusual plumage. The golden ear-tufts of the normal bird in summer plumage were absent and there were in their place stripes of pale chestnut, the feathers of which were of the length of ordinary feathers. The black feathers of the sides of the head and neck were also of ordinary length so that there was no appearance of a " tippet." The black of these parts and of the crown was not so glossy as in the other bird. Mr. Witherby, to whom I have submitted colour photographs thinks that the bird may have been in its first summer as he has examined skins of birds in similar plumage. Mr. Witherby adds that this plumage is little known and as such birds appear to be scarce it seems probable that only certain individuals acquire this undeveloped plumage. On June 18th I arrived at the hide at 2.45 p.m. Nothing of an unusual nature took place until 4.10 p.m., when I noticed the hen swimming towards the nest carrying a small quantity

2 VOL. XXXIII.] SLAVONIAN GREBE. 171 of material. This she placed on the edge of the nest, and carefully arranged. Then she leaped from the water on to the nest, and lowered herself as though to brood, but instead fell into the water again and swam from sight. Very shortly afterwards the cock followed exactly the same procedure. He had only just gone from sight when the hen reappeared " The cock leaned right forward and watched every movement made by the hen. The eartufts were not raised but only slightly spread." with more nesting material. After this had been placed into position the hen paddled backwards for a short distance, then, paddling rapidly forward, she leapt on to the side of the nest. Her next action is worthy of note, for she went through the motions of removing non-existent nesting material from the top of the single egg. There appears, therefore, to be a firmly implanted instinct both to cover and remove, which in this instance had functioned in the latter case, but not in the former. The hen then settled to brood.

3 172 BRITISH BIRDS. [VOL. xxxm. At 4.25 p.m. the hen, still brooding, began to call very excitedly and a moment later the cock emerged from the reeds just behind the nest. He also called excitedly, and it was noticed that on this occasion he did not carry any nesting material. The excitement became intense. The hen solicited by stretching out her head and neck, curving the latter in a snake-like manner, while the chin almost rested upon the surface of the water. Both called excitedly. The cock swam rapidly and jerkily round the nest, spreading and displaying the gorgeous golden-yellow ear-tufts. His head was jerked from side to side and bowed up and down. He stopped in front of the hen and bowed until his bill rested on the water, the ear-tufts being brought right forward so that their vivid colouring showed to best advantage. For some moments the cock remained like this, while the hen was motionless, looking straight at the cock as though hypnotized. Next the cock swam round the nest twice, then hesitated whilst at the rear of the hen. He proceeded to paddle backwards, then very rapidly forwards, and leaping out of the water jumped on the hen's back. With his large, white-lobed feet he smacked the shoulders of the hen alternately and very rapidly, after which coition took place. The hen remained prone all the time and the cock left immediately afterwards. She then readjusted the feathers along her back and continued to brood. I waited until 6.15 p.m. when the hen was still brooding and no further incident had taken place. On the following day, June 19th, I spent another period of observation in the hide, and again witnessed the courtship, display and mating, which was similar in every respect to that already described. There was, however, an interesting preliminary. I was left in the hide at p.m. and before my wife was out of sight the two Slavonian Grebes swam towards the nest, calling excitedly. Both carried nesting material. Several journeys were made and I noticed that the rotting vegetation used in the construction of the nest was collected from just beneath the surface of the water, In the middle of these operations, and while the hen was in the near vicinity of the nest, the cock stopped and displayed. He swam alongside the nest, but remained in the water, stretched out his neck, raised the golden-yellow ear-tufts and called. He remained in this attitude for some seconds before he continued to add nesting material. The hen took no notice of this display and had, in fact, continued building through it all. Shortly afterwards the hen came on to brood and the cock swam out on the loch.

4 VOL. XXXIII.] SLAVONIAN GREBE. 173 At 1.25 p.m. the hen left the nest and stayed away until 2,20 p.m., when she returned bringing a further supply of building material. She brooded until 2.45 p.m., when the cock swam into view. The display and mating then took place as already mentioned. At 3.10 p.m. a change over took place. As the cock approached the nest, the hen slipped off and swam into the reeds. The cock, instead of coming on to brood, stopped just behind the nest and remained there for over half an hour. He then collected further material which was piled on the side of the nest and at 3.50 p.m. came on to brood. Fourteen minutes later he left and set about nestbuilding once again. In five minutes he was back brooding again and remained so until 4.12 p.m. At this time he began to call and display while brooding the egg. His neck was stretched not downwards as formerly but upwards at an angle of about 45 degrees from the body and the ear-tufts were fully raised. During the display the hen arrived and swam rapidly backwards and forwards while collecting nesting material. She took little notice of the cock's behaviour, though the cock watched every movement she made with intense interest. The hen swam towards the hide and came within a foot of where I was sitting. The cock leaned right forward, still watching every movement but the ear-tufts were not raised, only slightly spread. The hen made for the reeds where she whinnied, and a few moments later the cock left the nest and joined her, at 4.20 p.m. It was not possible to keep a continual watch on this nest, but on June 21st I noticed that a second egg was laid, while oii the 25th there were three fresh eggs. Needless to say, by this time, the courtship and display had been discontinued, and it was interesting to note that since the laying of the second egg, the nest was covered whenever left. The original egg was left in the nest, and it was with regret that we had to leave the neighbourhood before witnessing the completion of the brooding and hatching. It is to be presumed that this particular pair of birds were unique in not recommencing the breeding cycle on being interrupted by the theft of most of their first clutch and in continuing to incubate the single egg during the courtship period. Although all Grebes add nesting material during the whole of the stages of incubation, this pair brought much more than normal, so that it would seem that they went through a partial phase of nest building concurrently with that of courtship and display, but the fact remains that the single egg held them to the original nest.

5 British Birds, Vol. XXXIII., PI. 4. DISPLAY OF SLAVONIAN GREBE UPPER : The cock displays his golden-yellow tufts as he bows his head in front of the hen. LOWER : The cock displays to the hen by swimming round her and raising his tufts and moving his head from side to side and up and down. (Photographed by Eric J. Hosking.)

6 British Birds, Vol. XXXIII., PI. 5. DISPLAY OF SLAVONIAN GREBE UPPER : The cock swam round the nest twice, then hesitated when behind the hen. LOWER : The cock stretched his neck upwards at an angle of about 45 0 from the body and the ear-tufts were fully raised. (Photographed by Eric J. Hosking.)