THE BEHAVIOR OF THE HORNED GREBE IN SPRING ROBERT W. STORER Museum of Zoology University of Michigan AM Arbor, Michigan 48104 The Homed Grebe (Podiceps uuritus) is a Great Grebe. The sympatry, particularly in widespread and common breeding bird in the Northern Hemisphere, has presumably re- the rolling pothole country of western North sulted in the evolution of specific differences America and suitable parts of northern Europe in the nuptial plumage and courtship patterns and Asia, yet almost nothing has been written which are effective in preventing hybridiza- about its behavior. The purposes of this paper tion and also differences in size, gregarious- are to describe the behavior of this species on ness, and feeding habits which may have re- the breeding grounds prior to egg-laying, to sulted in reduced competition. compare the behavior of this species with that The behavior of the Great Crested Grebe of related grebes, to offer suggestions con- is well known through the pioneering paper cerning the evolutio,n of some of the behavior of Huxley ( 1914 ) and Simmons ’ monograph patterns, and to compare behavioral with ( 1955). Papers by Wobus ( 1964) on the Red- other kinds of evidence relating to the phy- necked Grebe, by Mrs. McAllister (1958) on logeny of these birds. the Eared Grebe, by Nero (1959 and in Pal- The closest relatives of the Ho,rned Grebe mer 1962) on the Western Grebe, and by me are the Red-necked Grebe (Podiceps grise- (1963b) on the Great Grebe provide some gena), Great Crested Grebe (P. cristutus), basis for comparison, although none ap- Eared Grebe (P. nigricollis), Silver Grebe (P. proaches Simmons ’ study in completeness. occipit&) , and Taczanowskis’ Grebe ( P. Having had some field experience with all taczanowskii). The head patterns of these eight of the species concerned, I am fortunate species are shown in figure 1. Two other spe- in being able to make firsthand comparisons cies, the Great Grebe (“Podiceps” ma@r) and and to interpret the published work on these the Western Grebe ( Aechmophorus occiden- species. ta1i.s) are somewhat more distantly related to Although my interest in the Homed Grebe the Horned’ Grebe (Storer 1967) but are in- dates from the 1936s when I first watched cluded in the discussion. transients displaying in New Jersey, most of The Red-necked and Eared Grebes, like the the observations on which this paper is based Homed, have a Holarctic distribution, but the were made at potholes above the QuAppelle’ Eared also has isolated populations in Africa Valley of Saskatchewan in May and June 1959 and, formerly, in the Andes of Colombia. The and from 10 to 27 May 1966, and in the Minne- Great Crested Grebe is widely distributed in dosa pothole country of Manitoba from 4 to Eurasia, Africa, Australia, and New Zealand. 16 May 1967. These data were supplemented The Silver Grebe is found in much of tem- by observations made in several other years perate South America, ranging north in the since 1953 in North Dakota and Alberta and Andes to Ecuador; and Taczanowskis’ Grebe, by notes on wintering birds in California and a close relative of the Silver Grebe, is confined transients in Michigan. to Lake Junin at 13,400 ft elevation in Peru. Most of the observations were made from The Great Grebe is widely distributed in South a parked car, which proved a satisfactory America from southern Brazil and Peru to blind and was sufficiently large for operat- Tierra de1 Fuego, but unlike the Silver Grebe, ing both a motion picture camera and sound it is not found at high elevations. The Western equipment. Motion pictures have proved par- Grebe is found in western North America, ticularly valuable in describing complex be- ranging south to the Mexican Plateau. Thus havior and in preparing the figures. the Homed, Red-necked, and Eared Grebes For ease in analysis, the complex courtship are sympatric in varying combinations with ceremonies are broken down into simple pos- the Great Crested Grebe in Eurasia and with tures, movements, vocalizations, and displays. the Western Grebe in North America. In The terms “posture” and “movement” are used South America, both the Silver and Taczanow- for the simpler elements of more complex pat- skis’ Grebes occur on Lake Junin, and the terns. “Display” and “ceremony” are used in Silver Grebe is widely sympatric with the the sense of Simmons (1955:182), who adapted The Condor, 71:180-205, 1969 D801 BEHAVIOR OF THE HORNED GREBE IN SPRING 181 plumage. A. P. tacmnowskii, FIGURE 1. Heads of the six_ species of Podiceps, sen.s-us&i&o, in nuptial __ __ _ B. P. cristatus, (2. P. occipital& D. P. au&us, E. P. grisegenu, F. P. nigricolh. Vertical hatching, rufous (coarse) or red (fine); horizontal hatching, gray; stippling, yellow or buff. Huxleys’ usage (1914). The names used for of a lone bird, members of a pair can usually the comfort movements are taken from Mc- be distinguished when they are together. Kinney (1965) because these movements in The head plumes are conspicuous in dis- grebes are in general homologous with those plays and the positions of these plumes are in waterfowl and probably many other birds. integral parts of the displays. In the Cere- The other names for behavior patterns are monial Turning Away and the posture pre- largely taken from the works of Simmons and ceding the Weed Trick, all the plumes are Huxley. In a few cases I have coined new flattened against the head. The Furtive pos- names, hopefully using words which aptly ture is similar, except that the duck-tail is describe the behavior without implying pur- raised; the raising of the duck-tail may thus pose. be an expression of appeasement or anxiety. Of all kinds of behavior, courtship differs In Advertising, the tippets and horns are fully most from one species to another. I have spread vertically but little flared out, whereas therefore concentrated on studying and de- in Rearing and before, during, and dismo8unt- scribing this aspect. But because elements of ing after copulation, the tippets are fully courtship patterns were prosbably derived from spread and flared out so that they are almost day-to-day behavior, discussion of the latter at right angles with the sides of the head. is needed background for any discussion of At the height of the Penguin Dance and in the origins of courtship displays. the Weed Rush, the horns and tippets are held in a posture intermediate between those dur- THE NUPTIAL PLUMES AND DISPLAY ing Advertising and copulation. From this it seems likely that flaring of the horns and tip- In nuptial plumage Homed Grebes are strik- pets expresses a strong sexual component in ing birds. The neck and sides are bright displays. chestnut, and three groups of plumes adorn The function of the chestnut color of the the head: the rounded, black tippets, the buffy neck and sides is not clear. In part, it may lateral crests or “horns,” and the small, medial, be cryptic, for birds in nuptial plumage are black “duck-tail” on the crown. Males and far less conspicuous on the potholes where females are similar, but the females are they breed than birds in winter plumage smaller, their nuptial plumes are shorter than would be. It also may be part of the pattern those of the males, and the chestnut of the which functions in species recognition, for the neck and flanks often is paler and duller. Eared Grebe, the species which most resem- Thus, while it often is difficult to tell the sex bles the Homed on the breeding grounds, has 182 ROBERT W. STORER a black neck. The position of the line of de- Pre-flight behavior and taking-off were ob- marcation between the chestnut of the neck served at the same two potholes on the eve- and the white of the breast is probably sig- nings of 15 and 16 May 1966 between 20:30 nificant. At most times, the white of the under- and 22:O0. I have also seen this behavior on parts remains below the waterline, but in the Huron River, near Ann Arbor, Michigan. Advertising, when conspicuousness is advan- Three Homed Grebes were on the river shortly tageous, the head is stretched upward and after sunset on 20 April 1961. Two of the the white of the somewhat puffed-out breast birds, possibly paired, remained close together is prominent below the chestnut of the neck. on the water. About 19:27 ESTthe lone bird assumed the pre-flight posture and swam LOCOMOTION about, turning this way and that in a “nervous” Flying. On the breeding grounds, Homed fashion. Twice it dove, I thought with the Grebes fly more than one might expect. I wings slightly spread, wing-flapped, did at have observed them flying under at least four least two swimming-shakes, and once flapped sets of circumstances: approaching their mate across the water toward the pair before taking after a separation, attacking another bird, fly- off at 19:37. It did not circle but flew directly ing away from a pothole in the evening, and east over a railroad bridge, possibly landing flying upwind. Flying to the mate occurs beyond on the river. occasionally when members of a pair are sep- Upwind flights are seen on very windy days arated and one of them Advertises loudly. and serve to take the bird from the lee side Such a flight may result in a Discovery Cere- of a pothole to the windward one. I saw one mony in both the Homed and Red-necked male make such flights, once on the afternoon Grebes.