179 Climate and Weather Effects on Seabirds E. A. Schreiber CONTENTS 7.1 Introduction 179 7.2 Weather Effects on Fitness and Behavior 182 7.2.1 Fitness 182 7.2.2 Behavior 183 7.3 Weather Effects at the Nest 185 7.3.1 Effects on Timing of Breeding 185 7.3.2 Effects on Nest Sites 186 7.3.3 Effects on Care and Development of Eggs and Young 187 7.4 Weather Effects on Feeding 188 7.4.1 Effects on Finding and Transporting Food 189 7.4.2 Effects on Capturing Food 189 7.4.3 Effects on Prey Distribution 190 7.5 Types of Weather Events and Their Specific Effects 191 7.5.1 Long-Term Events 191 7.5.2 One- to Three-Year Events 192 7.5.2.1 El Niño–Southern Oscillation Events (ENSO) 193 7.5.2.2 La Niña Events 202 7.5.2.3 ENSO Have Shaped Our Thinking on Seabird Demography 202 7.5.2.4 ENSO and Weather Websites 203 7.5.3 Seasonal Weather Patterns 203 7.5.3.1 Seasonal Oceanographic Changes 203 7.5.3.2 Winter 204 7.5.3.3 Migration 204 7.5.4 Short-Term Weather Effects 204 7.6 Conclusions 205 Acknowledgments 206 Literature Cited 207 7.1 INTRODUCTION For a group of birds with similar life-history characteristics (deferred onset of breeding, long life, small clutch size, slow growth), seabirds live in a highly diverse variety of environments in their worldwide distribution. They experience the full gamut of weather patterns, whether daily, season- ally, annually, or on greater scales, and these patterns affect their survival, their habitat, their food supply, their ability to feed, and, thus, the continuing evolution of their species. 7 © 2002 by CRC Press LLC 180 Biology of Marine Birds Effects of weather on birds can be long term, occurring over hundreds of years, or as short as a passing rain storm. The long-term effects of weather on birds undoubtedly have help shaped their particular demography and other life-history characteristics. In the short term, weather effects on seabirds can be seen in more proximate factors: the decision to nest that year or not, where to nest, annual nest success, growth rates of chicks, and survival of adults. Weather can cause the extirpation of a species from an area or only the loss of a few eggs to chilling. It can affect birds directly through increased wind levels or rain causing difficulty in flying, through flooding of nests, and through thermal stress. Effects can also be indirect: weather parameters can alter or destroy nesting habitat, change fish or krill distribution, or cause decreased visibility of prey. Weather effects on seabirds are easy to observe on land but determining what is occurring while the birds are at sea has proven to be a difficult challenge, partly because our picture of how seabirds sample the ocean is incomplete. Seabirds primarily eat fish, squid, krill, and plankton that they must find and catch in the ocean, a medium that can exhibit dramatic variability or cycles from daily to seasonally to annually (see Chapter 6). Not only must seabirds feed in all these conditions, but during the nesting season, food must be transported back to the colony to feed young. Weather can affect: 1. Cost of catching food (Konyukhov 1997, Finney et al. 1999). 2. Transportation cost of food (Pennycuick 1982, Jouventin and Weimerskirch 1990, Fur- ness and Bryant 1996, Weimerskirch et al. 1997). 3. Ability of birds to find food (Dobinson and Richards 1964, Dunn 1973, Taylor 1983, Schreiber and Schreiber 1989, Cruz and Cruz 1990, Finney et al. 1999). 4. Timing of the breeding season (Nelson 1978, Anderson 1989, Schreiber and Schreiber 1989, Konyukhov 1997, Anderson et al. unpublished). 5. Number of birds that attempt to nest in a given season (Schreiber and Schreiber 1989, Duffy 1990, Warham 1990). 6. Clutch size (Springer et al. 1986, Coulson and Porter 1985). 7. Reproductive success and chick growth (Prince and Ricketts 1981, Gaston et al. 1983, Coulson and Porter 1985, Cruz and Cruz 1985, Schreiber and Schreiber 1993, Schreiber 1996, Arnould et al. 1996, Finney et al. 1999). 8. Thermoregulation (Howell and Bartholomew 1961, 1962, Bartholomew and Dawson 1979, Kildaw 1999). 9. Adult survival (Schreiber and Schreiber 1989, Duffy 1990, Chastel et al. 1993, Mon- tevecchi and Myers 1997). 10. Availability of food (Murphy 1936, Nelson 1978, Gaston et al. 1983, Arntz and Tarazona 1990, Montevecchi and Myers 1996, 1997, Finney et al. 1999). Unusual or severe weather can impose a burden on seabird populations. In the most severe cases, such as occur during El Niño–Southern Oscillation events (ENSO; Schreiber and Schreiber 1984, 1989, Ainley et al. 1988), many adults may die. ENSO events, a worldwide rebalancing of the heat load of the earth that causes extreme weather patterns, are discussed in detail below. Seabirds respond to anything that affects their food source and often can serve as a good indicator of fish availability (Bailey et al. 1991, Hunt et al. 1991, Montevecchi and Myers 1992, Montevecchi 1993). However, a confounding factor in using birds as indicators of fish availability is that some species of seabirds alter their feeding effort to adjust to changes in fish stocks in order to supply a more constant amount of food to chicks (Drent and Daan 1980, Finney et al. 1999). Other seabird breeding parameters may be useful as an indicator of fish stocks, such as length of feeding trips, growth rates of young, changes in the mass of adults, and reproductive energetics (Cairns et al. 1987, Ainley and Boekelheide 1990, Montevecchi and Myers 1992, Montevecchi 1993, Schreiber 1994, 1996). © 2002 by CRC Press LLC Climate and Weather Effects on Seabirds 181 Determining the effects of weather on seabirds and understanding the evolutionary implications of the documented short-term changes require long-term monitoring of banded individuals (Figure 7.1). Few studies have accomplished this. The Farallon Islands, one such example, are one of the best-studied seabird communities in the world and provide abundant data on the myriad effects of weather on seabirds. From 1971 through today biologists from the Pt. Reyes Bird Observatory monitored the approximately 300,000 individuals of 11 species nesting there (Ainley and Lewis 1974, Ainley and Boekelheide 1990). This long-term perspective has taught us much about seabird biology, the effects of the environment, and the vital importance of long-term studies. Notably, the population was not found to be stable and in equilibrium, contrary to what we have frequently been taught in the way most populations exist, at least until the 1982–1983 ENSO event (Schreiber and Schreiber 1989). ENSO events were one reason for the instability in population numbers found on the Farallons, but seasonal variation also was not constant from year to year, causing further variation in the population. Overlaid on this variability, photoperiod also had an effect on initiation of laying. Interestingly, when the originally planned 5- to 6-year study began, researchers thought they would find a normal pattern in most years. Thirteen years later, through severe ENSO, mild ENSO, severe droughts, and record rains, no two years were found to be the same (Ainley 1990). In the author’s own work in the Pacific, years used to be referred to as ENSO years and normal years. But, as the Farallon researchers found, no one prevailing pattern emerged in normal years! Long ago I began calling the years ENSO years and non-ENSO years, after coming to realize that the environment of seabirds was constant only in its inconsistency. General effects of weather on fitness in seabirds, weather effects at the nest, and effects on the feeding ability of birds at sea are discussed in this chapter. Finally, weather effects are addressed in terms of the length of the event: FIGURE 7.1 R. W. Schreiber bands a young Masked Booby on Christmas Island (Pacific Ocean). Long-term studies of individually marked birds are necessary to understanding seabird demography. (Photo by E. A. Schreiber.) © 2002 by CRC Press LLC 182 Biology of Marine Birds 1. Long-term effects (50 years or more) — ice ages, warming trends. 2. Annual and several years — individual ENSO events, La Niña. 3. Seasonal — air temperature, water temperature, wind levels, ocean current strength. 4. Short-term (weekly, daily) — hurricanes, rains, cloud cover, fronts. While weather events occur over varying lengths of time, the above divisions are not necessarily relevant to the effects experienced by birds in a particular region of the world. For example, ENSO events last from 1 to 2 or more years, but may exhibit only seasonal effects on birds in a particular area (Schreiber and Schreiber 1989). Because ENSO events begin in the tropical Pacific and have some of the most dramatic effects on birds there, the discussions below place particular emphasis on this area. Seabirds, having evolved over millions of years, have had their life histories shaped by the effects of weather, as well as other pressures of survival, all of which can alter their lifetime reproductive success. However, in many cases today, it is difficult or impossible for us to piece together cause-and-effect relationships in the evolution of seabird life histories in relation to weather or any other selective parameter. 7.2 WEATHER EFFECTS ON FITNESS AND BEHAVIOR 7.2.1 F ITNESS Seabirds have evolved adaptations that enable them to live in the oceanic environment quite successfully: they survive and reproduce in all areas of the world. During periods of “normal” weather patterns, seabirds appear essentially unaffected by weather, or at least are well adapted to tolerate local weather conditions. Yet, every aspect by which we measure fitness in a bird can be affected by severe or unusual weather: clutch size, adult mass, hatching success, chick growth, fledging success, presence of disease, population size, and survival. Not all seabirds in an area exhibit similar responses to any one weather event, possibly because they use different feeding areas, different feeding methodologies, a different food source, or have different flight capabilities. For instance, during strong ENSO events, most Masked Boobies (Sula dactylatra) on Christmas Island (central Pacific) desert the nesting colony at the very beginning of the event, while Red-tailed Tropicbirds (Phaethon rubricauda) and Great Frigatebirds (Fregata minor) do nest but lose many young to starvation as the event progresses and they cannot find enough food (Figure 7.2; Schreiber and Schreiber 1989). Within a seabird species, sexual differences may have evolved as adaptations to weather conditions and feeding in different areas. Wandering Albatrosses (Diomedea exulans) exhibit sexual segregation of foraging zones which can be explained by differences in wing-loading: males, with 12% greater wing-loading, feed in areas of highest wind levels (Shaffer 2000). Most seabirds are able to avoid some weather effects by flying to a different area, and this, in fact, is how many survive a storm. Albatrosses rely on, and apparently soar effortlessly in, heavy winds, and may even select nesting areas that have high wind levels to conserve energy (which can then be spent raising their young). On Midway Island (northern Pacific) Laysan (Phoebastria immutabilis) and Black-footed Albatrosses (P. nigripes) nesting inland in calm areas often walk to the edge of the island, where updrafts help them get airborne (Whittow 1993a, b). Field metabolic rates of Northern Fulmars (Fulmarus glacialis) were inversely related to wind level, perhaps account- ing for birds spending more time at the nest during calm periods (Furness and Bryant 1996). Wandering Albatrosses often sit on the sea and wait for higher wind levels to avoid the cost of flapping flight during calm periods (Jouventin and Weimerskirch 1990). Fulmars apparently could not afford the time to take the “sit and wait” approach and often suffered the increased costs of flight in low winds. Furness and Bryant (1996) suggested this as a factor that limits their breeding range. Assessing both direct (death) and indirect effects (such as decreased food supply or lost habitat) of dramatic weather patterns can be difficult. If banded populations exist, adult mortality may be © 2002 by CRC Press LLC Climate and Weather Effects on Seabirds 183 assessed directly, but few studies of seabirds have this luxury. A 27-year study of Snow Petrels (Pagodroma nivea) documented reduced adult survival in connection with ENSO events (Chastel et al. 1993). Population level (one of the most frequently measured parameters) may not always be a good direct indicator of the fitness of a local population since it can be affected by many parameters. For instance, changes in vegetation may make a colony site unsuitable for nesting, causing a decline in the number of birds in an area (Schreiber and Schreiber 1989). Dispersal, migration, and changes in food availability can also affect population size (Klomp and Furness 1992). Few studies have tracked a multispecies seabird community over time and attempted to explain why breeding numbers of individual species do not fluctuate in synchrony, and whether or not this reflects a degree of adaptedness. Differing responses of species to stochastic events may explain the proximate effects seen (Ainley and Boekelheide 1990, Schreiber and Schreiber 1989) but does not answer the question of a species fitness. Chick growth rate and fledging mass are sometimes directly correlated with survival to breeding age (Croxall et al. 1988, Chastel et al. 1993), perhaps the most important measure of a species fitness as a whole. Unusual variation in chick mass is generally a reflection of changes in the adults’ ability to feed brought on by weather (changes in oceanographic parameters) or changes in the distribution of the food resource, again, often itself brought on by weather (Konarzewski et al. 1990, Schreiber and Schreiber 1993). Weather is used here to mean either a short-term perturbation such as a storm, or a larger-scale event such as an ENSO, and to include oceanographic as well as atmospheric events. 7.2.2 BEHAVIOR Seabird adults and chicks use various behavioral methods to thermoregulate when overheated or chilled (Bartholomew et al. 1968, Bartholomew and Dawson 1979, Welty and Baptista 1988). To FIGURE 7.2 A young Great Frigatebird on Christmas Island (Pacific Ocean) calls to its arriving parent overhead. Last year’s dead chick lies beneath the nest. It was deserted by its parents in 1983, during one of the worst ENSO events on record. (Photo by R. W. and E. A. Schreiber.) © 2002 by CRC Press LLC 184 Biology of Marine Birds dispel heat when hot, they can fluff feathers or droop wings to increase circulation around them, pant (gular flutter) to provide evaporative cooling, seek shade, expose or shade certain body parts, or sit with their backs to the sun and hang their heads in their own shade or stand on a rock. Figure 7.3 illustrates the components of behavioral thermoregulation in Hermann’s Gulls (Larus heer- manni), shown in the order in which they appear as heat load increases (Bartholomew and Dawson 1979). Under the severest heat load, all behaviors are used together. Young of many species seek shade during the heat of the day if it is available (even that offered by their parents’ body; Howell et al. 1974, Konyukhov 1997, Schreiber et al. in preparation). Seeking shade may provide a less energetically expensive method of cooling rather than using physiological methods, an energy-conservation technique that may be important in times when food is limited. Wind level and panting rate are inversely correlated in Herring Gulls (Larus argentatus), implying an effective cooling function of wind (Baerends and Drent 1970). Frigatebird and booby chicks often raise their rear end toward the sun and tilt their upper body and head down low in their own shade during the heat of the day (Schreiber et al. 1996, Norton and Schreiber in press). Storks are known to defecate on their legs to provide evaporative cooling (Hancock et al. 1992), a behavior not common in seabirds although it is documented in Cape Gannets (Morus capensis; Cooper and Siegfried 1976). Desert birds, such as the Gray Gull (Larus modestus), are far more active at night, conserving their energy during the day (Howell et al. 1974). Rather than transferring FIGURE 7.3 Gulls and other seabirds use various behavioral methods to adjust to temperature. By adjusting its posture and the erection of its feathers, this gull goes from keeping warm in cooler temperatures to “cooling” postures in the heat of the day. (From Bartholomew and Dawson 1979, University of Chicago. Used with permission.) © 2002 by CRC Press LLC Climate and Weather Effects on Seabirds 185 heat to eggs or small chicks by direct contact, adults may stand over them in the heat of the day (Figure 7.4; Nelson 1965, Bartholomew 1966, Huggins 1941, Howell and Bartholomew 1962), though Baerends and Drent (1970) consider this an adult comfort movement that provides cooling. Frigatebirds, herons, storks, and some other species will stand, facing the sun, wings drooped and twisted so that the ventral surface faces the sun. This is most likely a thermoregulatory behavior although its function is not really understood. Some species drink water when hot (Schreiber et al. in preparation). During cold weather birds may hide their bills in feathers, shiver, or huddle in groups, and attentiveness by adults to eggs and chicks is increased (Bartholomew and Dawson 1979, Baerends and Drent 1970). Adults may sit tighter on the nest during cold spells or rain to not expose their eggs (Baerends and Drent 1970). 7.3 WEATHER EFFECTS AT THE NEST 7.3.1 E FFECTS ON TIMING OF BREEDING The ultimate reason for breeding at a particular time may be tied to food availability, but our ability to understand this connection is hampered by our inability to document the actual availability of food to seabirds. Little is known about changes in the abundance of fish populations through the year. In polar areas the breeding period of seabirds approaches the limit of available time to fit in a breeding cycle, and probably commences as soon as conditions allow. Commencement of nesting in polar through temperate areas varies closely with the arrival of spring weather in many species (Sladen 1958, Warham 1963, Gaston and Nettleship 1981, Williams 1995, Konyukhov 1997, Hatch and Nettleship 1998). Late winters cause delayed nesting due to snow and ice on the breeding grounds and to fish availability. In temperate habitats, while climate may allow a longer breeding season than in polar areas, adequate food may only be available during summer months. At lower latitudes, air temperature variations are small and may have less significance for the onset of breeding, but food is frequently still seasonally available which has important effects on timing of laying. Brown Pelicans (Pelecanus occidentalis) in Florida lay earlier in warm winters and cease laying when a late cold spell occurs, possibly because of the effects of cold weather on the fish (Schreiber 1980). On tropical Johnston Atoll (central Pacific Ocean; 16°N, 169°W), some species exhibit strict seasonality of nesting (Christmas Shearwaters, Puffinus nativitatus; Wedge-tailed Shearwaters, P. pacificus; Brown Boobies, Sula leucogaster; Brown Noddies, Anous stolidus; and FIGURE 7.4 Black Skimmers and other seabirds nesting in hot climates may rise up and stand over their eggs (or young chicks) during the heat of the day, shading them but not applying additional heat by incubating (or brooding) them. (Photo by E. A. Schreiber.) © 2002 by CRC Press LLC 186 Biology of Marine Birds Gray-backed Terns, Sterna lunata), while others do not (Red-footed Boobies, Sula sula; Sooty Terns; and White Terns, Gygis alba; Schreiber 1999). Since we know little about the at-sea feeding behavior of these species, we do not understand why they differ in their flexibility of laying. Oceanographic factors (most likely because of their affect on the food source) can alter the timing of the nesting season. At both high and low latitudes, unpredictable changes in food availability induced by environmental events cause changes in the onset of breeding and increased mortality of chicks and adults (Schreiber 1980, Duffy et al. 1984, Schreiber and Schreiber 1984, Croxall et al. 1988, Hatch and Hatch 1990, Chastel et al. 1993, Regehr and Montevecchi 1997, Finney et al. 1999). Chick mortality appears to be generally higher than adult mortality but we have few data from marked populations. When changes in local environmental conditions cause a decrease in the available food supply, adult seabirds often desert nests, going elsewhere to find food. Adults deserting young and allowing them to die of starvation during a hurricane or ENSO event permits these long-lived birds to reproduce in another year, and in years after that. There are a few reports in the literature of subannual breeding by seabirds, laying every 8 to 10 months (Ashmole 1963, Stonehouse 1960, Snow 1965a, Harris 1969, 1970, Diamond 1976, Nelson 1977, 1978). Some of the studies which documented these short breeding cycles were conducted during ENSO events, when we now know that the breeding season can be altered by changes in food availability. While, in areas of normally rich food supply such as the Humboldt Current, subannual breeding may occur (Swallow-tailed Gull, Creagrus furcatus; Harris 1970), careful examination of nesting cycles over a period of years is needed to determine periodicity of breeding. The normal cycle for most seabirds probably is annual, with leeway for adjustment according to the food supply. 7.3.2 EFFECTS ON NEST SITES Many species are probably selecting breeding sites based on weather–climate parameters such as degree of shade (Red-tailed Tropicbird, Clark et al. 1983), wind level (Adelie Penguin, Pygoscelis adeliae, Volkman and Trivelpiece 1981; Brown Booby, Schreiber 1999), density of grass (Sooty Tern, Schreiber et al. in preparation), or distance to open water during chick rearing owing to extensive ice pack (Emperor Penguin, Aptenodytes forsteri, Williams 1995). The selection of breeding sites that allows birds to save energy may become significant in times of low food availability when adults increase feeding effort in order to successfully raise young. Beyond this, effects of weather on nest sites vary, causing nests to be covered by blowing sand, flooded by tides or rain (Figure 7.5), or being destroyed by unstable substrate (Burger and Gochfeld 1990, Warham 1990, Schreiber 1999). Black Skimmers (Rhynchops niger) actively keep their eggs above drifting sand in windstorms (Burger and Gochfeld 1990). Ground nests in some areas get flooded in high spring tides or storms. Laughing Gulls (Larus atricilla) nesting in salt marshes build substantial nests, continue to add nest material throughout the breeding season, and repair damaged nests (Burger 1979). Repair and maintenance are often not enough, however, and nests may be lost to floods and storms. Burrow-nesting species (such as petrels and shearwaters) commonly suffer nest loss to rains flooding the nest and to subsequent erosion or collapse (Warham 1990). The largest Adélie Penguin colonies occur in areas where dispersal of fast sea-ice occurs early in the breeding season, allowing birds easier access to feeding areas (Stonehouse 1963, 1975). Hurricanes can destroy habitat, making it unusable for many years, and may thus cause decreased nesting numbers in philopatric species (birds that return to the same nesting area each year). If nest loss occurs early enough in the season, many species will relay (Dorward 1963, Amerson and Shelton 1975, Gaston and Nettleship 1981, Coulson and Porter 1985, Warham 1990, Schreiber and Schreiber 1993, Casey 1994, Schreiber et al. 1996), although this is apparently least likely in the Procellariiformes. When nest or chick loss occurs late in the season, few to no birds relay, possibly due to insufficient time to complete the cycle or because of energetic constraints, or both. © 2002 by CRC Press LLC Climate and Weather Effects on Seabirds 187 7.3.3 E FFECTS ON C ARE AND D EVELOPMENT OF E GGS AND Y OUNG Weather effects on breeding seabirds are confounded by factors such as adult age, adult experience, flexible time budgets of adults, and nest location (Drent and Daan 1980, Montevecchi and Porter 1980, Ainley et al. 1983, Cairns et al. 1987, Burger and Piatt 1990, Hamer et al. 1991, 1993, Croxall et al. 1992, Schreiber 1994, Falk and Moller 1997). Some data indicate that less experienced breeders are more affected by weather parameters which cause food shortages (Ainley et al. 1983), but due to a lack of known-age populations of seabirds, this has received little study. Females that lay a multiegg clutch sometimes lay fewer eggs during seasons with unusual weather patterns (Boekel- heide et al. 1990). In years with unusual ice conditions in the high Arctic, Northern Fulmars and Black-legged Kittiwakes (Rissa tridactyla) may not lay at all (Nettleship 1987, Baird 1994). Indi- vidual egg size is thought to be genetically constrained and unable to change significantly in response to climate variability, as has been found in some studies (Monaghan et al. 1989, Schreiber and Schreiber 1993, Schreiber 1999). But egg size does change with adult age, at least in some species, possibly obscuring any potential weather or food availability effects (Coulson and White 1958). In general, adults must protect eggs and small young (unable to thermoregulate yet) from both hot and cold temperatures (Sladen 1958, Howell et al. 1974, Ainley et al. 1983, Burger and Gochfeld 1990, Warham 1990, Schreiber and Schreiber 1993, Williams 1995, Schreiber et al. 1996), but there are few data on fatal temperatures for eggs or chicks. During very hot weather, adults may stand over eggs, shading them rather than transferring heat to them (Howell 1979). They may soak their belly with water and then sit on the egg (Howell 1979), although this might be done to cool the adult, rather than the egg (Baerends and Drent 1970), or both. In Antarctica, where it reaches –45°C and lower during the Emperor Penguin breeding season, the ability to keep eggs warm is vital to hatching success (Kooyman et al. 1971). Exceptionally high winds in Antarctica can actually blow eggs away during nest relief of penguin pairs, or blow the adults themselves away from their nest (Ainley et al. 1983). A drop in chick mass and increased mortality in small chicks are often related to precipitation and accompanying chilling (Nye 1964, Dunn 1975, Konarzewski and Taylor 1989). Small Red- tailed Tropicbird chicks on Johnston Atoll (central Pacific Ocean) experience higher mortality during rainy days (Schreiber 1999), chilling of the chick being the probable cause. A severe rainstorm in Newfoundland caused the death of 90% of the Herring Gull chicks present (Threlfall et al. 1974). Small chicks are also susceptible to short-term weather perturbations that cause difficulties for adults FIGURE 7.5 Burrowing nesting birds like this Magellanic Penguin chick may have their burrow flooded during severe storms. (Photo by P. D. Boersma.) © 2002 by CRC Press LLC 188 Biology of Marine Birds catching food since they cannot survive long without food. Year-to-year changes in reproductive success and chick growth rates have been related to changes in sea-surface temperatures worldwide (particularly during ENSO events: Boersma 1978, Springer et al. 1984, Murphy et al. 1986, Ainley et al. 1988, Croxall et al. 1988, Anderson 1989, Schreiber and Schreiber 1989, Duffy 1990, Warham 1990), probably due to changes in the distribution of fish. The effects of longer-term weather patterns on seabirds, such as brought on by ENSO events, are discussed below. The effects of various wind levels on adults’ ability to feed can be determined from measuring chick growth rates, but growth rate is also affected by the chicks’ energetic expenditure. Kidlaw (1999) found high wind levels resulted in reduced chick growth rates in Kittiwakes in extremely windy sites, while chicks in less windy sites grew normally. In a case such as this it is difficult to determine whether adults had difficulty feeding chicks in the windier sites or the windier sites increased chicks’ energetic expenditure. Persistent pack ice cover in Antarctica (probably due to low winds, such as occurred in 1968–1969) causes desertion of nests by Adelie Penguins (Ainley et al. 1983). In normal years the sea ice disappears at about the time chicks hatch, allowing shorter foraging trips by adults. Here again, however, experience of adults plays a role that overlies the role of the environment: more experienced adults delivered more food to chicks during difficult feeding times (Ainley and Schlatter 1972). The harsh environment of polar regions often causes the loss of eggs and chicks when nests get snowed in, ice freezes eggs to ledges, or the pack ice does not melt in time (Ainley et al. 1983, Nettleship et al. 1984, Hatch and Nettleship 1998, Warham 1990). Chicks of many species breeding in cold climates undergo long periods of fasting and still survive (Tickell 1968, Wasilewski 1986, Warham 1990, Hatch and Nettleship 1998). Red-tailed Tropicbird chicks on Christmas Island (central Pacific) grow more slowly and do not reach an asymptotic mass during ENSO events, but still fledge successfully at the normal fledging mass, taking longer to do so (Schreiber 1996). Audubon’s Shearwater (Puffinus lherminieri) chicks in the Galapagos required from 62 days (non- ENSO years) to 100 days (ENSO years) to fledge (Harris 1969). This flexibility in chick growth rates appears to be a common adaptation in seabird chicks of all orders to survive variable weather patterns (Harris 1969, Mougin 1975, Ainley et al. 1983, Warham 1990). Severe weather or dead calm during the period of fledging can be perilous for young birds as they first learn to fly. Fledgling albatrosses in the north Pacific often get stranded on the beach during days of low wind levels and appear to be dependent on high winds to take their first flights (Fisher and Fisher 1969). Many reports of wrecks of beached birds (mass mortality) are dispro- portionately young birds (Harris and Wanless 1984, Piatt and van Pelt 1997, Work and Rameyer 1999), possibly reflecting the difficulty young birds have learning to fly and feed themselves. 7.4 WEATHER EFFECTS ON FEEDING The broad variation in seabird flight style and abilities leads to a wide variety of feeding methods, and while there are data on the effects of weather on birds in their colonies, the data for how it affects birds at sea are scant. Most often, our knowledge is derived from what we can measure on land. Weather affects the ability of seabirds to find food due to: (1) wind speed and direction and precipitation affecting flight; (2) cloud cover, precipitation, clarity of water, and turbidity of water affecting their ability to see and capture their prey; and (3) its effects on prey behavior and distribution (Dunn 1973, Taylor 1983, Sagar and Sagar 1989) . The energetic cost of flight has not been studied in many seabirds (see Chapter 11) and studies can be difficult to carry out. When a bird is at sea, out of sight of land, it is not easy to determine how much time is spent sitting on the water vs. actively diving or swimming after food vs. flying. Various devices, such as activity recorders, have been developed to help determine amount of time spent on the water and number of dives made during a trip to sea (Cairns et al. 1987, Schreiber 1996, Arnould et al. 1996). While these devices can assist in determining the © 2002 by CRC Press LLC [...]... Weak 18 57 1862 1864 1866 1 871 1 873 1 877 –1 878 1880 1884–1885 18 87 1888 1891 1896 1899–1900 1902 1905 1911–1913 1914 19 17 1919 Weak Weak Weak Weak Strong Weak Strong Weak Strong Moderate Strong Moderate Strong Moderate Moderate Strong Moderate Strong 1923 1925–1926 1929–1930 1932 1939–1941 1943–1944 1950–1951 1953 19 57 1958 1963 1965 1969 1 972 –1 973 1 976 –1 977 1982–1983 1986–19 87 1990–1994 19 97 1998 Weak... E.J Tarbuck 1995, The Atmosphere, Prentice-Hall, Englewood Cliffs, NJ Used with permission.) © 2002 by CRC Press LLC Climate and Weather Effects on Seabirds 1 97 TABLE 7. 1 Years of El Niño–Southern Oscillation Events (ENSO) and Strength of Event Year Strength Year Strength Year Strength 172 6 172 8 176 3 177 0 179 1 1803–1804 1814 18 17 1819 1821 1824 1828–1829 1832 18 37 1844–1846 1850 1852 1854–1855 Moderate... influence of Sargassum “reefs.” Auk 103: 141–151 HANEY, J C 1989 Remote characterization of marine bird habitats with satellite imagery Colonial Waterbirds 12: 67 77 HANEY, J C., AND D S LEE 1994 Air-sea heat flux, ocean wind fields, and offshore dispersal of gulls Auk 111: 4 27 440 HARRINGTON, B A., R W SCHREIBER, AND G E WOOLFENDEN 1 972 The distribution of male and female Magnificent Frigatebirds, Fregata... inter- and intra-colony variation Canadian Journal of Zoology 61: 2465–2 475 © 2002 by CRC Press LLC 210 Biology of Marine Birds GIBBS, H L., AND P R GRANT 19 87 Ecological consequences of an exceptionally strong El Niño event on Darwin’s finches Ecology 68: 173 5– 174 6 GOCHFELD, M., AND J BURGER Family Sternidae (terns) Pp 624–666 in Handbook of Birds of the World (J del Hoyo, A Elliott, and J Sargatal,... coast of Florida American Birds 26: 9 27 931 HARRIS, M P 1969 Food as a factor controlling the breeding of Puffinus lherminieri Ibis 111: 139–156 HARRIS, M P 1 970 Breeding ecology of the Swallow-tailed Gull (Creagrus furcatus) Auk 87: 215–243 HARRIS, M P 1 973 The biology of the waved albatross Diomedea irrorata of Hood Island, Galapagos Ibis 115: 483–510 HARRIS, M P., AND S WANLESS 1984 Breeding success of. .. ecology of the red-footed booby in the Galapagos Journal of Animal Ecology 38: 181–198 NELSON, J B 1 977 Some relationships between food supply and breeding in the marine Pelecaniformes Pp 76 – 87 in Evolutionary Ecology (B Stonehouse and C Perrins, Eds.) University Park Press, London NELSON, J B 1 978 The Sulidae: Gannets and Boobies Oxford University Press, Cambridge NETTLESHIP, D N 1 977 Studies of seabirds... fuscata) In The Birds of North America (A Poole and F Gill, Eds.) The Birds of North America, Inc., Philadelphia SCHREIBER, R W 1980 Nesting chronology of the eastern Brown Pelican Auk 97: 491–508 SCHREIBER, R W., AND E A SCHREIBER 1984 Central Pacific seabirds and the El Niño–Southern Oscillation: 1982–1983 perspectives Science 225: 71 3 71 6 © 2002 by CRC Press LLC 214 Biology of Marine Birds SCHREIBER,... (Oceanodroma furcata; Boersma et al 1980) See Chapter 6 for a full discussion of seasonal changes in oceanography and food availability © 2002 by CRC Press LLC 204 Biology of Marine Birds 7. 5.3.2 Winter At high latitudes, winters bring on severe weather conditions as well as low temperatures, and both affect seabirds To some extent mid- and high-latitude marine birds are adapted to the commonly occurring... Additionally, population levels may be in a constant state of flux brought on by stochastic weather patterns, as suggested by Schreiber and Schreiber (1989) © 2002 by CRC Press LLC 206 Biology of Marine Birds FIGURE 7. 16 Long-term studies of individually marked birds are vital to further our understanding of the ecology and demographics of seabirds This Masked Booby on Johnston Atoll (Pacific) is getting... rates of breeding Northern Fulmars Ecology 77 : 1181–1188 GASTON, A J., AND D N NETTLESHIP 1982 The Thick-billed Murres of Prince Leopold Island — a study of the breeding biology of a colonial high arctic seabird Canadian Wildlife Service Monograph Series 6, 350 pp GASTON, A J., G CHAPDELAINE, AND D G NOBLE 1983 The growth of Thick-billed Murre chicks at colonies in Hudson Strait: inter- and intra-colony . Food 189 7. 4.2 Effects on Capturing Food 189 7. 4.3 Effects on Prey Distribution 190 7. 5 Types of Weather Events and Their Specific Effects 191 7. 5.1 Long-Term Events 191 7. 5.2 One- to Three-Year. the continuing evolution of their species. 7 © 2002 by CRC Press LLC 180 Biology of Marine Birds Effects of weather on birds can be long term, occurring over hundreds of years, or as short as a. Strong 176 3 Strong 1864 Weak 1929–1930 Moderate 177 0 Strong 1866 Weak 1932 Weak 179 1 Strong 1 871 Strong 1939–1941 Strong 1803–1804 Strong 1 873 Weak 1943–1944 Weak 1814 Strong 1 877 –1 878 Strong