87 Colonial Breeding in Seabirds John C. Coulson CONTENTS 4.1 Introduction 87 4.2 What Is a Seabird Colony and What Are Its Limits? 89 4.3 Functional Structure of a Colony 90 4.4 Theories of the Functions and Advantages of Colonial Breeding 92 4.4.1 Shortage of Nesting Sites 92 4.4.2 Defense against Predation 92 4.4.3 A Colony Is a Safe Place 94 4.4.4 Social Stimulation 94 4.4.5 Wynne-Edwards’ Concept of Self-Regulation 96 4.4.6 Food-Finding and the Colony as an Information Center 96 4.4.7 Adjustment of the Breeding Season 97 4.5 Recent Hypotheses 98 4.5.1 Richner and Heeb — Group Foraging 98 4.5.2 Danchin and Wagner — Quality Separation 98 4.5.3 Danchin and Wagner — Sexual Selection 98 4.5.4 Danchin and Wagner — Commodity Selection 99 4.6 Disadvantages in Colonial Breeding 99 4.7 Characteristics of Colonial Seabirds and Seabird Colonies 100 4.8 Synchrony 107 4.8.1 Comparison between Colonial and Noncolonial Species 107 4.8.2 Age Effects and Synchrony 108 4.9 Is Colonial Breeding Always an Advantage? 108 4.10 Future Research 109 Literature Cited 109 4.1 INTRODUCTION The word “colony” has several different definitions. Its use with respect to seabirds should not be confused with the meaning when applied to human society, where, from Roman times, it has indicated a group of people under the jurisdiction of a country some distance away. In a zoological sense, “colony” describes a group of individual organisms that live close together. It also carries an implication of communication and collaboration, resulting in positive (beneficial) interactions between individuals. In ornithology, the term is usually restricted to a group of individuals at a breeding site, while “flock” is applied to birds which are gregarious at other times of the year or when away from the breeding site. Several authors have considered practical definitions of a colony (Buckley and Buckley 1979, Kushlan 1986, Kharitonov and Siegel-Causey 1988), but others have not readily accepted these definitions, mainly because they do not apply to all species or they include implications that have not been fully researched. In mathematical terms, the individuals in 4 © 2002 by CRC Press LLC 88 Biology of Marine Birds a colony are clumped or aggregated in space, with other apparently suitable areas remaining unoccupied more frequently than would be expected by chance. One of several methods of dem- onstrating this is to show that, on average, the nearest neighbor to each pair or nest is significantly closer than would be expected by chance. In sessile organisms such as corals and sponges, the colony is a permanent group, persisting for the lifetime of the individuals and often for longer. The characteristic of permanence is also applicable to many seabird colonies, but in this case it is because of the breeding-site tenacity of many adult birds, the stability of the nesting area, e.g., cliffs and islands, and also because successive generations are attracted to the same colony sites. There is a further important difference between a colony and a flock of birds. In a colony, the pairs have the same neighbors, in the same spatial positions for most of the breeding season. In many species, many of the individual neighbors are retained in successive breeding seasons. In a flock, a bird rarely retains the same neighbor for more than a few minutes, although in some species, such as geese and swans, pairs and family groups often remain together within flocks. These differences between a flock and colony are important because in the former, the change of position limits to a much greater extent the potential complexity of behavior and other interactions that could develop between individuals, whereas in a colony, interactions between the same neighboring individuals can develop and accumulate over time and present an opportunity for more complex interactions and effects to develop. In birds, almost all species which are colonial can readily be identified as such by their spatial distribution (Figure 4.1). In most cases, there is no practical problem in recognizing which are colonial species; the clumping of nests is obvious and the individuals or pairs are in close proximity. However, in a few species which nest some distance apart from each other, actual measurement may be required to confirm that the nearest neighbor is closer than would be expected by chance. For example, the distance between pairs of some “great albatrosses” and Bonaparte’s Gulls (Larus philadelphia) may be 100 m or more, but despite this distance, the nest sites are still clumped, with many apparently suitable nesting areas remaining unoccupied. The term “loosely colonial” (Cramp and Simmons 1977) has been applied to such situations, but this term is not very helpful because it is descriptive rather than functional and fails to take into account the manner in which the birds communicate and react with each other. The important question is “To what extent do neighboring pairs interact?” and this still needs to be investigated. Colonial breeding in seabirds has been discussed and reviewed on several occasions, particularly by Gochfeld (1980) and Wittenberger and Hunt (1985), while Brown and Brown (1996) and Orians (1961) have considered it in land birds. FIGURE 4.1 Australian Gannet colony illustrating a dense colony in which birds nest about a beaks’ distance apart resulting in the necessity for frequent communication among neighbors to signal intentions. (Photo by J.B. Nelson.) © 2002 by CRC Press LLC Colonial Breeding in Seabirds 89 It remains to be established whether the selective pressures which are and have been involved in colonial breeding in seabirds are similar in other birds, and in colonial mammals, such as seals and bats. In many animals, there are considerable disadvantages in living close to each other. This is the basis of density-dependent mortality and reduced breeding success. Colonial breeding pre- sumably only occurs when the disadvantages are outweighed by advantages in coloniality, at least in the long term. Adverse density-dependent effects have not yet been reported in seabirds, but this may simply reflect the difficulty of studying such effects at sea and away from colonies. This chapter includes reviews of the published literature on colonial breeding in seabirds. It leans heavily on studies over 40 years on Black-legged Kittiwakes (Rissa tridactyla), not primarily because it is the main study animal of the author, but because parallel studies on other seabird species are often yet to be made. It also includes personal experience and thoughts, and unpublished analyses on the topic. This author would have liked to include more between species comparisons, but as yet there are insufficient data on colonial breeding in most seabirds, and until more studies are available, in-depth between-species analyses of aspects of coloniality are not possible. 4.2 WHAT IS A SEABIRD COLONY AND WHAT ARE ITS LIMITS? Essentially, a seabird colony is a group of breeding individuals which associate together and maintain the association to an extent that is greater (often much greater) than that expected by chance. Such a group needs a mechanism to maintain the grouping and some form of communication is necessary to achieve this. In many cases, the approximate limits of a colony are obvious because of the large distance between that group and the next. But the practical problems of recognizing whether there are one or more functional groups (= colony) involved where huge numbers of birds nest together are not easily determined. The use of “subcolony” or similar terms indicating sub- groups (e.g., Buckley and Buckley 1972, Gochfeld 1979, Burger and Shisler 1980) may be useful in some respects. However, in cases where this term has been used, the interactions, if any, between the subgroups have not been investigated and the opportunity in these studies of understanding the functioning of colony structure as a whole has not been grasped. When birds in a colony are spread out over a relatively large area, doubts may exist as to whether the group exists as a functional unit. To maintain a group or colony, some form of communication is necessary. Difficulties in achieving this exist when the birds are separated by physical features of their nesting area, e.g., around a headland sea cliff or on each side of a hill, and where all of the birds cannot see or hear each other. Such situations beg the practical question of “When does a colony become two colonies?” Fundamentally, it is to be expected that there is direct or possibly an indirect interaction between the individuals within a colony, and, in some cases, simple observa- tions of the responses birds make to each other can resolve the extent of a colony. Often, interaction between birds in a colony is by sight and this is evident in the silent “panic flights” of some terns and gulls, where all of the individuals respond virtually simultaneously and synchronously, even without the external stimulus of a predator. There are also vocal interactions, evident by the waves of calling which repeatedly spread through colonies of some species, e.g., Common and Thick-billed Murres (Uria aalge and U. lomvia), some gulls, penguins, and albatrosses. It is very likely that calls play a particularly important part in communication in species which visit the colony at night, such as in the small petrels and other species which nest in dark areas such as caves, under boulders, and in burrows. It is conceivable that smell and even sonar responses may also be important in some nocturnal species, although this is an area which still requires more critical research and experiment. Most diurnal species use calls and postures as a means of communicating (see Chapter 10), so that cliff-nesting seabirds which spread around a headland, or ground nesting species on both sides of a ridge, have pairs which are unlikely to be able to communicate with all others (unless the species is one which has aerial displays). Some Herring Gull (Larus argentatus) “colonies” extend continuously for over 2 km (Chabryzk and Coulson 1976, Burger and Shisler 1980), and Black- © 2002 by CRC Press LLC 90 Biology of Marine Birds legged Kittiwake colonies sometimes spread around headlands and also can extend for several kilometers. In such colonies, the birds at each end of the group are most unlikely to be in direct communication. Yet the use of “subcolonies” is not really a helpful term because when used, the methods of interaction are not normally considered and the term is usually used in an arbitrary manner, for example, to achieve constancy during surveys, e.g., Northern Fulmar (Fulmarus gla- cialis) (Fisher 1952) and Black-legged Kittiwake (Coulson 1963). 4.3 FUNCTIONAL STRUCTURE OF A COLONY Coulson and Dixon (1979) made a study of the functional nature and structure of Black-legged Kittiwake colonies, relying on the behavior of the birds to indicate the area within which the birds constituted an association. Early in the season, when birds first returned to the colony, social behavior was primarily limited to “panic” or “dread” flights from the colony. The birds on cliff nesting sites over distances up to several hundred meters would frequently, spontaneously, silently, and synchronously leave the breeding areas on the cliffs. Such responses are, apparently, synchro- nized by vision; the synchrony was lost when different groups of birds could not see each other. At this time of year, and at the end of breeding season, a series of such panic flights often synchronously terminated the daily occupation of the colony. At the beginning of the breeding season, kittiwakes occupy a colony for parts of several days. They become less nervous, panic flights stop, and the distances between interacting individuals becomes restricted to much shorter distances. At this stage, the main interactions occur only between pairs and small groups of pairs, and are solely triggered by the greeting ceremony performed between members of a pair. These greeting ceremonies result in the characteristic social outbreak of “kittiwaking,” calling among groups of pairs. In contrast, solitary birds on nest sites (i.e., birds whose mates are temporarily away) usually show no or only minimal reaction to a greeting ceremony performed by a neighboring pair. Detailed studies of kittiwakes based on this response show that the social reaction between pairs extended for less than 2 m (Coulson and Dixon 1979), and rarely produced responses between pairs 5 m or more apart (Figure 4.2). This greeting reaction had a number of characteristics: 1. Each individual pair was stimulated more frequently if there were many pairs in close proximity (within 2 m), i.e., where the nest density was high. 2. The reaction by other pairs to an arrival and reuniting of the focal pair was over a very limited distance, but when considered over a period of time, the reactions linked the members of a colony together. 3. The timing of breeding in the kittiwake was closely correlated with the density of other pairs immediately around a nesting pair (Coulson and White 1960). It is presumed that this difference was the result of differences in the frequency of greeting ceremonies arising from the density of nesting birds. 4. The density of neighboring pairs tended to be lower at the edge of the colony, since other pairs were absent from the edge side, more potential nest-sites were unoccupied, and, as a result, the overall density was usually lower. 5. By inference, isolated pairs will receive little of this “social” stimulation from other pairs of kittiwakes and will be appreciably delayed in display and nest-building. As a result, breeding by isolated pairs is inhibited. (The same inhibitor also prevents relaying in pairs which have lost their eggs, resulting in relaying being restricted to early breeders, which lose their eggs soon after laying.) These results explain a number of the characteristics of breeding in kittiwake colonies and also identify the nature of the structure within a kittiwake colony. They explain why the spread of breeding in Black-legged Kittiwake colonies is closely linked with the maximum density in the © 2002 by CRC Press LLC Colonial Breeding in Seabirds 91 (a) (b) FIGURE 4.2 The responses of other pairs of Black-legged Kittiwakes to the reuniting of a pair in relation to distance between nests. (a) The probability in relation to distance of a particular pair responding to the reuniting of the focal pair. (b) The number of pairs responding at given distances from the focal pair which are reunited and engage in mutual courtship. The thick line indicates low density areas and the thin line high density areas. The data from high and low density areas are significantly different (p < 0.01), indicating that birds at high density make more responses, although they may actually respond to a small proportion of the times that other pairs reunite in their immediate neighborhood. (After Coulson and Dixon 1979.) Distance apart (m) 0 0 0.2 0.4 0.6 0.8 0.3 0.6 0.9 1.2 1.7 2 Probability of pair responding Distance (m) 0 0.3 0.6 0.9 1.2 1.7 2 0 0.4 0.8 1.2 Pairs responding © 2002 by CRC Press LLC 92 Biology of Marine Birds colony (Figure 4.3) where laying takes place first, and that laying ends synchronously in all neighboring colonies, since all have some low density areas. These observations were particularly valuable in giving an insight into the functional structure of a colony. In a kittiwake colony there is a very short distance over which successful breeding birds, even when changing mates, will normally change nesting sites (Coulson and Thomas 1983, Fairweather and Coulson 1995). 4.4 THEORIES OF THE FUNCTIONS AND ADVANTAGES OF COLONIAL BREEDING 4.4.1 S HORTAGE OF N ESTING S ITES One of the earliest suggestions as to why some birds nest in colonies was that they use nesting sites which are extremely limited in space and, as a result, they crowd together. While some colonial species have precise nest-site requirements and nest in very restricted areas, many show only broad requirements found in many places. For many species, it is difficult to envisage that in the past, suitable nesting sites were sufficiently scarce to force individuals to nest very close together, unless numbers were many times greater than now. The size and extent of some colonies are huge, but it is difficult to believe that alternative nesting areas do not exist, and this view is supported by species which are currently spreading to new areas and forming new colonies. However, some oceanic species have very few land areas on which to nest, yet have vast oceans over which to feed. This may be the reason for large numbers of Greater Shearwaters (Puffinus gravis) nesting on two islands in the Tristan da Cunha group and on Gough Island, where some pairs are apparently forced to lay above ground (Rowan 1952). But why this species does not breed elsewhere on other islands within its range is not known. 4.4.2 DEFENSE AGAINST PREDATION There is much information showing the effect of large numbers intimidating or confusing the predator by the high density of potential prey. Colonies of Arctic (Sterna paradisaea) and Common Terns (S. hirundo) show the effect of large numbers of animals in reducing the effectiveness of FIGURE 4.3 The variation in local density of nests in two Black-legged Kittiwake colonies. Note that both colonies have a proportion of nests at low density and the colonies differ by the maximum density reached. Breeding starts first at high density (at the left) and last at low density (at the right). Thus the spread of breeding is greatest in the colonies with the highest local densities. These effects are shown in the spread of breeding in two actual colonies in Figure 4.6. (After Coulson and White 1960.) 25 20 15 10 5 0 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Percentage Density (nests per 1.7 m radius) © 2002 by CRC Press LLC Colonial Breeding in Seabirds 93 predators (Hamilton 1971). For example, a territorial predator may exclude others of its own species, so there may be many prey in a colony but few predators to exploit them. Other effects operate through confusing or repeatedly diving at the heads of predators. Avian predators may be harried in flight by a group of terns, but the attacks are much less successful when only a few terns are involved. There is, however, a paradox about colonial breeding having evolved as an anti-predator device, since most colonies are situated in places free or relatively free from predators. Colonies on sea cliffs, in trees, on islands, and even on buildings are in situations which reduce or totally avoid predation by mammals. It seems surprising that colonial breeding should be evolved as an anti-predator device when the species involved choose to breed in localities relatively free from predators. In any case, the nature of the predator determines the likely outcome of a predation attempt. A predator wanting a single item of prey has to find the whole colony before obtaining its meal. In contrast, a predator which needs to take several prey items for a single meal is probably made to search harder and longer if the prey is evenly spread out and not colonial. Large predators, such as man, dogs, and foxes, are little deterred by diving Common Terns and species of crested terns do not even intimidate mammalian predators by swooping at them. Royal Terns (Sterna maxima) seem to be unable to defend their eggs from Laughing Gulls (Larus atricilla; Buckley and Buckley 1972) and Arctic Terns are unable to defend their eggs against individual European Starlings (Sturnus vulgaris) and Ruddy Turnstones (Arenaria interpres; J. C. Coulson unpublished). While some bird species have developed a social defense against certain predators by breeding in a colony, it seems unlikely that predation was the common factor responsible for development of colonial breeding in the first place. Frank Fraser Darling (1938), in his book Bird Flocks and the Breeding Cycle, envisaged colonial breeding as an anti-predator device that produced a selective advantage as a result of colonial birds breeding more synchronously. He believed that the greater the size of the colony, the greater the synchrony, and hence the reduced impact of predators by swamping them with a temporary overabundance of prey, producing a higher breeding success (Figure 4.4). He provided quantitative evidence from studies on Herring Gull and Lesser Back-backed Gull (Larus fuscus) colonies, but his sample sizes were relatively small and the results did not show statistically significant differences in breeding success between large and small colonies. FIGURE 4.4 A diagrammatic representation of Darling’s idea of synchrony of breeding reducing the impact of predation. The horizontal line represents the daily requirements of predators; through synchrony, the proportion of chicks taken by the predator is less in the more synchronized than in the less synchronized colony. This diagram should be compared with Figure 4.7 which shows actual results from two Black-legged Kittiwake colonies. Number of young Date © 2002 by CRC Press LLC 94 Biology of Marine Birds 4.4.3 A COLONY ISA SAFE PLACE Subadult birds visit their natal colony and other colonies prior to breeding as they make a decision on where to breed, although little is known about the actual decision-making process. Presumably, a safe nesting site is an important factor in such a decision and the presence of young is a good indicator of this. Individuals of many species are highly philopatric, returning to breed where they hatched, while others move into colonies elsewhere (see discussion of philopatry in Section 4.7, number 9). 4.4.4 SOCIAL STIMULATION Work by MacRoberts and MacRoberts (1972) on Herring and Lesser Black-backed Gulls found no evidence of socially induced synchrony in colonies. In contrast, Parsons (1976) showed that synchrony occurred within, but not between, 52 small areas of about 12 m × 12 m within a Herring Gull colony. He also found that breeding was earliest in central and latest in peripheral areas of the colony. The statistically significant differences were mainly caused by synchronous breeding in old birds within small areas. The later breeding in young birds, which tended to be a high proportion of those breeding at the periphery, also contributed to this effect. Parsons (1975) also demonstrated that the highest hatching success in this species was among those individuals breeding when most of their neighbors were at a similar stage of breeding (Figure 4.5), thus able to swamp predators (in this case, cannibal Herring Gulls) with excess food. Overall, very early and late laying pairs were much less successful. He went on to demonstrate this effect was indeed relative to the time of breeding of neighbors and not to actual date by field experiments which altered the timing of breeding. When substantial groups were delayed by egg removal, the time of optimal breeding was also delayed, but again was highest when synchronous with most of the immediate neighbors (Figure 4.6). The fact that the time of peak of breeding success moved shows clearly that success was not linked with a peak of food availability for the parents (and as is the case in Great Tits Parus major; Perrins 1970), but to a social effect within the colony. Re-examination of the “social stimulation effect” in the Black-legged Kittiwake produced very different findings to those of Darling. Larger colonies are less synchronous, the opposite of that expected from the Darling effect (Coulson and White 1956; Figure 4.7). More detailed investigation on kittiwakes showed that local density, and not colony size or age composition, was the important FIGURE 4.5 The hatching success in Herring Gulls in relation to the percentage of pairs nesting in each 4- day period. The correlation is r 7 = 0.92 and is highly significant (p < 0.01). The points in the bottom left-hand corner of the graph include both early and late breeding birds. Hatching success is highest in those birds which laid when many other individuals also laid. (After Parsons 1975.) % pairs nesting over 4-day period % hatching success 0 5 10 15 20 25 50 55 60 65 70 75 80 © 2002 by CRC Press LLC Colonial Breeding in Seabirds 95 FIGURE 4.6 The fledging success in Herring Gulls laying on different dates in a control (squares and thick line) and an experimentally delayed colony (triangles and thin line) about 200 m apart. The birds in the experimental group were delayed by removing early laid eggs. In both cases, the highest success is among those breeding relatively early in each colony and so receiving protection from their immediate neighbors with eggs and chicks. Note the appreciable difference in the fledging success of the two groups which laid between 26 May and 2 June. The main cause of loss was caused by a small number of cannibal Herring Gulls. (After Parsons 1975.) FIGURE 4.7 The timing of breeding in two neighboring Black-legged Kittiwake colonies. Note the different time of first appearance of young, but that the last chicks appeared at the same time. Thus breeding was less synchronous in the large colony, contrary to Darling’s concept (after Coulson and White 1958). These colonies are those showing the distribution of nest density in Figure 4.3. Days after 1 May 2 6 10 14 18 22 26 30 34 38 42 46 50 0 10 20 30 40 50 60 % chicks fledging Days after 1 June 1 0 50 100 150 200 250 300 350 400 450 9 17253341495765738189 Number of nests with young © 2002 by CRC Press LLC 96 Biology of Marine Birds factor and that breeding was earlier in dense groups, although at all densities, late breeding occurred in young birds breeding for the first time (Coulson and White 1958). Colony size as such was not the important factor envisaged by Darling, and local density within the colony was the key to the timing of breeding. Less-detailed investigation of other species has sometimes shown differences in timing and spread of breeding between colonies, e.g., Ashmole (1963) and Hailman (1964). While differences found have been explained by the Darling effect, these studies did not by themselves demonstrate the existence of the social stimulation effect, and these authors have been unable, for example, to exclude differences in the age composition of birds or in environmental conditions if colonies are situated some distance apart. 4.4.5 WYNNE-EDWARDS’ CONCEPT OF SELF-REGULATION Wynne-Edwards (1962, 1986) applied his views of social interactions between individuals and groups to animals as a whole and colonial breeding was seen by him as just one of the many ways animals can evaluate and respond to their own numbers. His ideas have been severely criticized (e.g., Elton 1963, Lack 1966), mainly because he invoked group selection (reduced breeding success by each pair for the benefit of the group) as the mechanism. The concept of group selection, apart from where kin (related individuals) are involved, is contrary to the outcome expected through natural selection. His ideas that animals may self-regulate their own numbers have not been effectively tested. It is extremely difficult to plan and execute such experiments while at the same time eliminate other variables. As a result, most of the attempts to examine and test this potential effect have been flawed and illustrate the advantages of applying Occam’s Razor (the concept of testing the simplest hypothesis first before testing a more complex one) to research. It is possible that some of the effects Wynne-Edwards proposed could actually be produced by natural selection. For example, there is much evidence that social interactions impose a constraint on where individuals can nest in colonies, with some individuals forced into using poorer nesting sites, or prevented from breeding until a later year. Physical sites of good quality are not in short supply, but become so when the birds have to select from within the limits of the colony. This results in an overall reduction of the reproductive output per pair. This type of effect has been reported in the Shag (Stictocarbo aristotelis; Potts et al. 1980) and Black-legged Kittiwake (Figure 4.8; Coulson 1971). Similar reduced reproductive output is produced by delaying the age at first breeding, e.g., Herring Gull (Chabryzk and Coulson 1976) and albatrosses (Warham 1990, Tickell 2000), induced by the high density of birds within colonies. How these situations became established by selection in the past is irrelevant; they can and do occur and have the effect of reducing reproductive output when numbers and density in the colony are high. It must be pointed out that in most seabirds, a colony is not synonymous with a population, the latter usually being composed of several, and often many, colonies. Thus control or limitation of the size of a colony will not necessarily regulate the size of the population because surplus individuals can move and produce new colonies. Coloniality may regulate the size and growth of a colony; it is much more doubtful that it can regulate the overall numbers of the species. 4.4.6 FOOD-FINDING AND THE COLONY AS AN INFORMATION CENTER Suggestions that colonial breeding facilitates exploitation of food sources are probably untenable, even in cases where food is highly clumped. The hypothesis that birds concentrate to breed at the place that minimizes the mean distance traveled between the nest and foraging locations (mentioned in Danchin and Wagner 1997) is perhaps not an adequate explanation since the position of food sources can change over time and so would need the optimal breeding sites to change in parallel, a situation that does not seem to occur frequently. © 2002 by CRC Press LLC [...]... breeding may be related to the nature of the food supply or the distribution, abundance, and method of feeding of predators, or the presence of parasites 4. 7 CHARACTERISTICS OF COLONIAL SEABIRDS AND SEABIRD COLONIES There are a number of characteristics of colonial seabirds, most of which occur in the majority of colonial species and some also occur in noncolonial breeding birds Sixteen characteristics are... herodias Behaviour 51: 99–1 34 KUSHLAN, J A 1986 Colonies, sites and surveys: the terminology of waterbird studies Colonial Waterbirds 9: 119–120 © 2002 by CRC Press LLC 112 Biology of Marine Birds LACK, D 19 54 The Natural Regulation of Animal Numbers Clarendon Press, Oxford LACK, D 1966 Population Studies on Birds Clarendon Press, Oxford LANGHAM, N E P 19 74 Comparative breeding biology of the Sandwich Tern... Scientific Report 1: 141 –1 94 ROWAN, M K 1952 The Greater Shearwater Puffinus gravis at its breeding grounds Ibis 94: 97–121 SCHREIBER, E A., AND R W SCHREIBER 1993 Red-tailed Tropicbird, in The Birds of North America 43 (A Poole and F Gill, Eds.) The Birds of North America, Inc., Philadelphia SCHREIBER, E A., R W SCHREIBER, AND G A SCHENK 1996 Red-footed Booby, in The Birds of North America 241 (A Poole and... Association 5: 123– 140 AUSTIN, O L 1 948 Predation by the common rat Rattus norvegicus in the Cape Cod colonies of nesting terns Bird Banding 19:60–65 BOULINIER, T., E DANCHIN, J.-T MONNAT, C DOUTRELANT, AND B CADIOU 1996 Timing of prospecting and the value of information in a colonial breeding bird Journal of Avian Biology 27: 252–256 © 2002 by CRC Press LLC 110 Biology of Marine Birds BROWN, C R.,... in Seabirds 99 FIGURE 4. 9 A colony of Laysan Albatross on Midway Island Generally older birds nest in the center of a colony and younger birds on the edges (Photo by R.W and E.A Schreiber.) 4. 5 .4 DANCHIN AND WAGNER — COMMODITY SELECTION Danchin and Wagner (1997) suggest a third possible explanation of colonial breeding, that of “commodity selection,” which tends to be an integration of several of the... temperature, distribution of fish, and breeding in seabirds over large © 2002 by CRC Press LLC 98 Biology of Marine Birds areas (see Chapter 7) Coulson (1985b) suggested that colonial breeding allows more effective adjustment of the breeding season to environmental conditions One of the characteristics of colonial birds is that in most species, isolated, solitary pairs are incapable of breeding Breeding... to sites at the edge of the colony Some are unsuccessful in obtaining a site and these produce a pool of nonbreeding birds characteristic of most colonies, the size of which has been suggested to be an indicator of the health of the colony and the population (Porter and Coulson 1987) These social pressures also may exert a limit to the growth of a colony as the ratio of edge-to-central area declines... Press, Cambridge COULSON, J C., AND E WHITE 1956 A study of colonies of the Kittiwake Rissa tridactyla (L.) Ibis 98: 63–79 COULSON, J C., AND E WHITE 1958 The effect of age on the breeding biology of the Kittiwake Rissa tridactyla Ibis 100: 40 –51 COULSON, J C., AND E WHITE 1960 The effect of age and density of breeding birds on the time of breeding of the kittiwake Rissa tridactyla Ibis 102: 71–86 COULSON,... gulls Rissa tridactyla L Journal of Animal Ecology 45 : 205–213 CRAIK, J C A 1995 Effects of North American Mink on the breeding success of terns and smaller gulls in west Scotland Seabirds 17: 3–11 CRAIK, J C A 1997 Aspects of the biology of the Common Gull Larus canus from remains left by predators Ringing and Migration 18: 84 90 CRAMP, S., AND K E L SIMMONS 1977 Birds of the Western Palearctic Oxford... and adaptive value of reproductive synchrony in colonial sea -birds Pp 207–270 in Behavior of Marine Animals Vol 4 Marine Birds (J Burger, B L Ollo, and H E Winn, Eds.) Plenum Press, New York GREENWOOD, P J 1980 Mating systems, philopatry and dispersal in birds and mammals Animal Behaviour 28: 1 140 –1162 GWINNER, E 1989 Photoperiod as a modifying and limiting factor in the expression of avian circannual . Advantages of Colonial Breeding 92 4. 4.1 Shortage of Nesting Sites 92 4. 4.2 Defense against Predation 92 4. 4.3 A Colony Is a Safe Place 94 4 .4. 4 Social Stimulation 94 4 .4. 5 Wynne-Edwards’ Concept of. of nest density in Figure 4. 3. Days after 1 May 2 6 10 14 18 22 26 30 34 38 42 46 50 0 10 20 30 40 50 60 % chicks fledging Days after 1 June 1 0 50 100 150 200 250 300 350 40 0 45 0 9 17253 341 495765738189 Number. actual results from two Black-legged Kittiwake colonies. Number of young Date © 2002 by CRC Press LLC 94 Biology of Marine Birds 4. 4.3 A COLONY ISA SAFE PLACE Subadult birds visit their natal colony