MÄURI ORA, 1979, 7: 151-155 151 COLOUR VISION IN THE PROCELLARIIFORMES (NOTE) PETER C. HARPER Department of Extension Studies, University of Canterbury, Christchurch, New Zealand ABSTRACT Observations at sea showed that some petrels perceive colour. The advantages of colour vision for these birds are discussed, and the need for further studies is stressed. Because flying birds pass so rapidly through their environment, they must be able to identify their food with speed and decisiveness. Clearly they must also avoid colliding with any object in their line of flight. Studies (see Sillman 1973) have shown that birds have a keenly perceptive vision. Colour is also an important Visual Stimulus for birds which must either choose between a green un-ripe berry and a red ripe one, or advertise themselves to a potential mate by means of a bright and gaudy plumage pattern. Intuition would suggest and experimental data provide evidence that diurnal birds perceive a colour spectrum similar to that of humans (e.g. Hamilton and Coleman 1933). Albatrosses and petrels of the order Procellariiformes are a group of marine birds with an ancestry of some 80 million years (Harper 1978). Not only are they noted for the size diversity, but also for their sombre plumage pigments. Black, browns, greys and blues are often in contrasting combinations with white, such that patterns would seem to preclude the need for colourful feathering. A coloured plumage would render the birds conspicuous to their predators both at sea and on land. Moreover, since most petrels also court and mate outside their subterranean burrows at night, a colourful plumage would appear unnecessary for courtship displays. It is perhaps for these reasons that the question of colour vision in petrels has received so little attention. During a 2.5 year Programme of ornithological research in southern seas aboard the Antarctic Research Ship Eltanin I discovered evidence to suggest that albatrosses and some petrels can detect colour. Whenever the Eltanin stopped for up to 30 hours on Station while scientific observations were made, the attending seafowl gathered in the water near the ship's stern to await the food scraps from the galley. The albatrosses (family Diomedeidae), whose size and aggressiveness gave them 152 MAURI ORA, 1979, Vol. 7 Status over the smaller species, were the first to search the floating debris whenever it was thrown overboard. There was a strong selectivity in the way in which the birds explored the multicoloured rubbish. Their first choice was pieces of orange peel, which the albatrosses quickly swam towards and seized in their beaks. A 3 to 8 second delay followed while the birds apparently tested the palatability of their prize, before it was dropped and ignored. The orange peel was not eaten. Following the larger birds such as the wandering albatrosses Diomedea exulans, or giant petrels Macronectes spp., the smaller procellariids took up the orange peel. Groups of Cape pigeons Daption capense quarrelled noisily over each piece before eventually leaving it to drift away. Wilson1s storm petrels Oceanites oceanicus darted to the orange peel and poised to peck it several times before flitting off. Other orange or red items received similar attention, such as bits of carrot, the plastic wrappings of processed meats and red cigarette packets (see colour photo p 39: Harper & Kinsky 1978). The remaining garbage was sampled until something edible (such as vegetable greens or slices of bread) was found. Following an initial savouring these were promptly eaten. Using the limited shipboard resources, I decided to see whether the birds would choose any particular colour if a variety was offered to them, and whether they were perhaps perceiving a particular brightness rather than colour. Five samples of each of 10 colours were made from coloured paper crushed into a small compact shape about 30 mm in diameter and concurrently offered to the birds. Observations and recording lasted until samples attracted no further attention or drifted out of view (up to 45 min). Grey samples with the equivalent light reflectance of orange and red were chosen with the aid of a Photographie lightmeter and a colour temperature meter (manufactured by Gossen, W. Germany). The results of three tests carried out in the Antarctic Atlantic (63°S, 40°W, 12 Feb. , 1966), the Antarctic Pacific (61°13 S/ 156°E, 9 Feb. 1967) and the Tasman Sea (45°S, 147°15,E, 25 Feb. 1967) are shown in Fig.l. My data are strongly biased towards those seavenging species which are attracted to ships (Pachyptila desolata is an exception). Moreover, some of the paper samples disappeared from view under the stern of the ship, while others were contested by so many birds that counting them was impossible. Given these and other obvious limitations, however, my experiments suggest that some Procellariiformes show preference towards particular colours, notably orange and red, with pink, yellow, blue white and green in descending order of choice. Giant petrels Macronectes spp., which showed little obvious colour discrimination, were the only species which attempted to eat the paper samples: the seavenging abilities of these birds are well known. Two questions arise from my observations. Why the preference for the above colours and what possible advantage does colour vision give the marine birds? Invertebrates rieh in carotenoids are eaten by both albatrosses and smaller petrels. Albatrosses are known to HARPER - PROCELLARIFORMES COLOUR VISION 153 Test 1 Test 2 Test 3 Antarctic Atlantic Antarctic Pacific Tasman Sea black grey brown L blue 0 green yellow agh ahj orange af ghi j adfhj ac df red af hj af h j pink af i adf white fg 0 10 20 30 O 10 20 O 10 NUMBER OF --POSITIVE RESPONSES Fig. 1 Positive responses of sqavenging Procellariiformes to different coloured objects. A positive response is active pecking at a paper object and each response noted relates to a different bird. a = Diomedea exulans (wandering albatross), b = D. epomophora (royal albatross), c = D. cauta (white -capped mollymawk)., e = Phoebetria palpebrata (light-mantled sooty albatross), f = Macronectes giganteus (giant petrel), g = Thalassoioa antarctica (Antarctic petrel), h = Qaption capense (Gape pigeon), i = Pachyptila desolata (Antarctic prion), j •= Oceanites oceanicus (Wilson's storm petrel). capture deep-water Bentho.phausia s.p. which are up to .120 mm in length and bright orange in colour (Harris 1973; Harper pers. obs.). The smaller euphausiids such as the Antarctic krill Euphausia superba which are eaten in great numbers by many oceanic petrels and albatrosses are also reddish-orange in colour. Presumably the birds were -attra.et.ed to the coloured paper samples because they represented a familiär food source of a similar colour. The birds are capable, • moreov-ez,, öf ^detecting the edibility of an object within a few seconds of picking it from the water. This would suggest that Visual p_ero.eption.can be used initially to find food (especially by day), and that other senses such as olfaction and touch might confirm whether or not it can be eaten. The smell of food is known to attract petrels from afar (Murphy 193 6). 154 MÄURI ORA, 1979, Vol. 7 The conspicuous bill and gape colours of the majority of the albatrosses and other surface-nesting species are comparable with the colour of their food prey. Combinations of orange, red, pink and yellow are the principle bill and gape pigments of the Diomedeidae and surface-nesting genera such as Thalassoica and Fulmarus. Gaping as courtship and threat display is widespread among surface-nesting petrels (Fig. 2) (e.g. Johnstone et al. 1975). The blue paper sample which attracted a light-mantled sooty albatross Phoebetria palpebrata in Test 2, is one key colour which distinguished this southern species from its more northern counterpart P. fusca. The differing sulcus colours of Phoebetria are probably as important to the birds as they are to taxonomists. Fig. 2 Billing and gaping behaviour of the white-capped mollymawk (Diomedea cauta cauta). The bill is pale greenish grey with yellow tips to both mandibles. There is a fleshy orange stripe from just in front of the eyes to the base of the bill that is displayed prominently during gaping behaviour. Photograph D. Milledge The pigments present in the Procellariiformes are also visually conspicuous in surface-nesting penguins - order Sphenisciformes. Burrowing penguin species are like most petrels not so colourful; bill gape and iris colours are often red or orange, and bright yellow superciliary crests are a feature of the eudyptid penguins. Prominent orange bill patches in conjunction with expansive orange markings on the necks of boi HÄRPER - PROCELLARIFORMES COLOUR VISION 155 emperor and king penguins (genus Aptenodytes) are both handsome and distinctive. Clearly the whole subject of colour vision in the marine birds is one ripe for a detailed investigation by Students of seabird ecology and behaviour. Also, it might be a fruitful avenue for comparative taxonomic studies. The purpose of this paper is to stimulate a more thorough analysis which will supersede this Contribution. LITERATURE CITED HAMILTON, W.F. and C0LEMAN, T.B. 1933. Trichromatic vision in the pigeon as illustrated by the spectral hue discrimination curve. Journal of Comparative Psychologe 15: 183-191. HARPER, P.C. 1978. The plasma proteins of some albatrosses and petrels as an index of relationship in the Procellariiformes. New Zealand Journal of Zoology 5(3): 509-549. HARPER, P.C. and KINSKY, F.C. 1978. Southern Albatrosses and Petrels: an identification guide. Price Milburn, Wellington. 116 pp. HARRIS, M.P. 1973. The Biology of the Waved Albatross Diomedea irrorata of Hood Island, Galapagos. Ibis 115(4): 483-410. JOHNSTONE, G.W., MILLEDGE, D. and D0RWARD, D.F. 1975. The white-capped albatross of Albatross Island: numbers and breeding behaviour.