Fledging Period Research Articles

Effects of Natal Departure and Water Level on Survival of Juvenile Snail Kites (Rostrhamus Sociabilis) in Florida

Abstract Survival rate from fledging to breeding, or juvenile survival, is an important source of variation in lifetime reproductive success in birds. Therefore, determining the relation-ship between juvenile survival and environmental factors is essential to understanding fitness consequences of reproduction in many populations. With increases in density of individuals and depletion of food resources, quality of most habitats deteriorates during the breeding season. Individuals respond by dispersing in search of food resources. Therefore, to understand the influence of environmental factors on juvenile survival, it is also necessary to know how natal dispersal influences survival of juveniles. We examined effects of various environmental factors and natal dispersal behavior on juvenile survival of endangered Snail Kites (Rostrhamus sociabilis) in central and southern Florida, using a generalized estimating equations (GEEs) approach and model selection criteria. Our results suggested yearly effects and an influence of age and monthly minimum hydrologic levels on juvenile Snail Kite survival. Yearly variation in juvenile survival has been reported by other studies, and other reproductive components of Snail Kites also exhibit such variation. Age differences in juvenile survival have also been seen in other species during the juvenile period. Our results demonstrate a positive relationship between water levels and juvenile survival. We suggest that this is not a direct linear relationship, such that higher water means higher juvenile survival. The juvenile period is concurrent with onset of the wet season in the ecosystem we studied, and rainfall increases as juveniles age. For management purposes, we believe that inferences suggesting increasing water levels during the fledging period will increase juvenile survival may have short-term benefits but lead to long-term declines in prey abundance and possibly wetland vegetation structure.

Sex differences in Little Auk Alle alle parental care: transition from biparental to paternal‐only care

Understanding differences in male and female care in biparental care systems can help interpret the selective pressures that shape parental strategies. We examined Little Auk Alle alle parental care at a breeding colony during the chick‐rearing and fledging periods by conducting observations on marked, known‐sex pairs, and by examining the sex ratio of birds carrying food to the colony. Little Auks transitioned from biparental to mostly paternal‐only care during late chick‐rearing. Males delivered more meals and spent more time at the colony than females during late chick‐rearing. Very few females were present at the colony by the end of chick‐rearing and through the fledging period, and all marked parents observed accompanying their chick to sea were male. Chick mass loss prior to fledging was associated with the lack of provisioning by the female parent, rather than a reduction in feeding frequency by both parents. The occurrence of paternal‐only care during and after fledging is discussed in relation to physiological, ecological and phylogenetic constraints.

The breeding biology of the Critically Endangered Seychelles Scops-owl Otus insularis: consequences for conservation and management

The endemic Seychelles Scops-owl Otus insularis is a Critically Endangered restricted-range species currently recorded only from the montane forest of Mahé, the largest (152 km2) and highest (903 m) island in the granitic Seychelles. Limited research has been conducted on the species and, in particular, details of its breeding biology are poorly known. Behavioural observations were made on 12 pairs by the systematic monthly use of playback of conspecific calls, in conjunction with frequent non-playback territory visits from April 1999 to May 2001. A total of eight nests, including the first nest record, were found on three territories. All were in tree cavities (7–25 m high) and contained either a single egg or chick. This was consistent with additional observations of solitary fledglings (n = 11, from eight territories). Incubation lasted 3–4 weeks and the fledging period was 4–6 weeks (data from two nests). The timing of copulations, in conjunction with the detection of nests and fledglings, suggests that the scops-owl can breed throughout the year with peaks in nesting occurring around May and October. Sex roles during breeding were similar to those of other Strigidae owls: incubation was performed by the female; males courtship-fed the female prior to and during incubation, and the female and chick for the first 2 weeks post-hatching; and both parents fed older chicks and fledglings. Fledglings remained on territory for at least 3 months. Breeding success of study pairs was low: two of eight nests were successful and 11 fledglings (recorded from eight of 12 study territories) were observed in a 26-month period, equivalent to c. 0.5 fledglings per territory per year. Evidence suggests that alien predators may have been a factor limiting breeding success. We discuss the conservation implications of our findings.

Space utilization by a cormorant ( Phalacrocorax carbo L.) colony in a multi-wetland complex in relation to feeding strategies

In this study, we investigated the response of inland breeding cormorants Phalacrocorax carbo to a complex spatial configuration of feeding habitats in relation to social and individual feeding strategies. The numbers of feeding trips outside the colony site (Lake Grand-Lieu, western France), where only solitary fishing is used by cormorants, and the number of birds fishing on the lake where social fishing predominates were investigated during the breeding season and compared with the fledging period. From the investigation of feeding trip traffic, we identified three major habitats used by cormorants in the vicinity of the colony site ( < 25 km around the colony site) that accounted for 94.1 of the IN flights and 92.0% of the OUT flights ( n=1745 arrivals and 2404 departures respectively), and notably one area that accounted for 58% of total flights although it is the furthest away. No fundamental change in the relative significance of these feeding grounds for solitary fishing cormorants was found throughout the breeding season, even in a between-years comparison (1996–2001), in contrast to what has often been found elsewhere. Although the peak of foraging activity in the surrounding habitats and also within the lake waters largely coincided with the time when the majority of young had fledged, the index of cormorant numbers (ratio between bird numbers at a given time and that for a baseline date) on the lake remained at a high level until late August compared to movements outside the lake, as a result of regular social fishing (84.9±4.0% of fishing numbers). From these findings, we discuss factors governing the selection of feeding grounds throughout the breeding season in relation to energy considerations, feeding strategies and food resources. To cite this article: J.-M. Paillisson et al., C. R. Biologies 327 (2004).

Plasma thyroid hormone pattern in king penguin chicks: a semi-altricial bird with an extended posthatching developmental period

Plasma concentrations of thyroid hormones (TH) were investigated during the extended posthatching developmental period (∼11 months) of a semi-altricial bird species, the king penguin ( Aptenodytes patagonicus). The first period of growth in summer was marked by a progressive rise in plasma T 4 concentration that paralleled rapid increases in body mass and in structural and down growth. By contrast, plasma T 3 concentration had already reached adult levels in newly hatched chicks and did not change thereafter. Circulating TH of king penguin chicks thus follow an original pattern when comparing to altricial and precocial species. During the austral winter, the long period of undernutrition of king penguin chicks was characterized by a decrease in circulating TH that can be related to a seasonal stop in growth and energy saving mechanisms. Plasma TH concentrations increased again during the second growth phase in spring, and they reached their highest levels at the end of the fledging period, slightly before juveniles initiated their first foraging trip at sea. As expected, plasma T 4 levels were elevated when chicks moulted, developing a true-adult type waterproof plumage. The data also suggest that T 4 plays a major role in skeletal development and pectoral muscle maturation in anticipation of marine life. Plasma T 3 was at its highest during the period when juveniles improved resistance to cold waters by going back and forth to the sea, suggesting a role for circulating T 3 in cold acclimatization occurring at that time.

Breeding biology of the Greyheaded Parrot (Poicephalus fuscicollis suahelicus) in the wild

The Greyheaded Parrot breeds in Northern Province, South Africa and south-east Zimbabwe (the southern limit of its range) from April to August, yet further north breeds in other months of the year. Egg laying between monogamous pairs is synchronous and 2–4 eggs are laid in natural cavities in Baobabs (Adansonia digitata.) Post-breeding seasonal movements occur into regions where nest sites are scarce or possibly absent. Males provision the female in the nest cavity during incubation and the early stages of nestling development. Attendance at the nest by the female is reduced once fledglings are able to thermoregulate on their own. By the end of the fledging period visitation rates to the nest site by the male and the female are reduced to twice a day (mid-morning and late-afternoon). Nest sites are possibly limiting, with interspecific competition for nest sites occurring. Intraspecific competition for nest sites in areas where populations have declined has possibly been reduced. Removal of chicks from nests by humans threatens populations outside protected areas. The conservation of this species in the southern limit of its range is thus highlighted.

Reproductive traits of marine terns (Sternidae): evidence for food limitation in the tropics?

Marine terns breed between 80°N and 70°S, making them a suitable group for examining links between latitude and reproductive traits. We investigated such traits for 34 taxa in seven genera, using analyses of residuals to correct for effects of e.g. female body mass and egg mass on other life history traits. Both tree- and K-means clustering, based on four traits excluding chick provisioning mode, identified two groups of terns—those that breed on tropical oceanic islands and those that breed along mainland coasts and at temperate islands (>40° from the Equator). Among mainland terns, there is a tendency for reduced clutch investment at low latitudes both between and within species. There is no interspecific latitudinal variation in incubation or fledging period of these terns, but intraspecific variation in fledging period (longer in the tropics) has been reported for one species. Tropical island terns, which mostly breed at sites lacking native ground predators, show extreme clutch reduction and lay a single, relatively large egg that has a long incubation period. Fledging periods are also long, despite the fact that these are the only terns to use multiple prey loading or regurgitation to feed their chicks. These patterns are interpreted as responses to low food availability stemming from a combination of low oceanic productivity, high bird densities because of breeding space limitation and localised prey depletion associated with central place foraging.

The breeding biology of Hutton's Shearwater

Hutton's Shearwater, Puffinus huttoni, is a small endangered seabird that breeds at only two sites in the Seaward Kaikoura Mountains, New Zealand. The alpine habitat has restricted access and research on the species’ breeding ecology. The extreme breeding habitat may also impose reproductive costs on Hutton's Shearwaters because of the energy needed to fly to colonies. Within the Kowhai Valley colony burrows were located on moderate to steep-angled slopes wherever the soil was deep and friable enough to burrow. Available breeding habitat may be a factor limiting the population. Breeding burrows were generally simple and non-branched. Males were larger than females in all measured body dimensions (bill length, bill depth, bill width, head length, head width and tarsus length), with the exception of wing length. Egg-laying within the colony was non-synchronous and took up to 38 days. The peak of egg laying occurred around 8 and 9 November in the 1998/99 and 1997/98 seasons respectively. The incubation period lasted for an average of 50.3 days and chicks fledged at an average age of 83.8 days. This fledging period is longer than that reported for the closely related Manx Shearwater, Puffinus puffinus. There were seasonal differences in the rate of mass gain by Hutton's Shearwater chicks. Mass gain by Hutton's Shearwaters was lower than that found in Manx Shearwaters and this may explain the extended fledging period. However, generally the results indicate that, despite the high altitude and extreme location of the breeding colonies, the breeding biology of Hutton's Shearwater fits the pattern observed in other species of Puffinus.

Breeding behaviour and performance of the Knysna Warbler Bradypterus sylvaticus on the Cape Peninsula, South Africa

Three pairs of Knysna Warblers were monitored on the south-eastern slopes of Table Mountain during the 2000 breeding season. Males displayed alone on territories until the second half of August, when females arrived. Nest-building (8 days) and incubation (16 days) were undertaken entirely by the female, who was not fed on the nest by the male. Chick provisioning was done mainly by the male. Arachnids and terrestrial amphipods were the most common prey brought to chicks. The fledging period was 12 days. Modal clutch size was three eggs, and depredation rates of eggs and chicks were high. After losses, replacement clutches were laid on average 19 days later, after a new nest was built. A maximum of three clutches per pair was recorded. Of 18 eggs monitored, 28% hatched and 17% fledged, equating to a production of one fledgling per pair per year. Ten days after fledging, the entire family leaves the territory, males probably returning once young are independent. The main threats to the local populations are clearing of riparian undergrowth and management practices that impact the predators of rodents.

Body Size and Timing of Fledging of Atlantic Puffins in the Faeroes and Northwest Norway

Abstract We studied the way, timing and diurnal rhythm of young Atlantic Puffins (Fratercula arctica) leaving colonies in NW Norway and Faeroes. The colonies differed in nesting habitat and predatory pressure. Both adult and young Puffins from Bleiksoy were significantly larger and heavier than those from Nolsoy. Young birds left the Bleiksoy colony about ten days later in the season, but considerably earlier during the night (22.00-04.00 h; peak: 00.00-01.00 h) than those on Nolsoy (24.00-0600 h; peak: 02.00-03.00 h). The fledging period was more synchronized on Bleiksoy, both within the season and on particular nights. Body mass and size of young puffins leaving the colony tended to decrease through the fledging period. Well-developed young birds from sloping parts of the Bleik colony flew down to the sea, while those from the lower-lying, flatter parts of the colony and those in poor condition walked to the sea. Fledglings which left on the wing reached the sea about one hour earlier and could fly beyo...

Prefledging Energy Requirements in Shorebirds: Energetic Implications of Self-Feeding Precocial Development

AbstractUnderstanding ecological consequences of avian developmental modes requires knowledge of energy requirements of chicks of different positions in the precocial–altricial spectrum, but those have rarely been measured in birds with self-feeding precocial young. We studied prefledging energy budgets in chicks of Black-tailed Godwit (Limosa limosa) and Northern Lapwing (Vanellus vanellus) in the field and in the laboratory. Lapwings show slower growth than godwits, reaching a 29% lower fledging mass (142 vs. 201 g) in a 32% longer period (33 vs. 25 days). Daily energy expenditure (DEE), measured by the doubly labelled water (DLW) technique, and daily metabolized energy (DEE plus energy deposited into tissue) increased proportionally to body mass at similar levels in both species. Total metabolized energy (TME) over the fledging period was 8,331 kJ in godwits and 6,982 kJ in lapwings, 39 and 29% higher than an allometric prediction (Weathers 1992). That suggests that self-feeding precocial chicks have high energy requirements compared with parent-fed species, due to costs of activity and thermoregulation associated with foraging. Those components made up 50–53% of TME in the shorebirds, more than twice as much as in seven parent-fed species for which DLW-based energy budgets are available. In captive lapwings and godwits growing up under favorable thermal conditions with food readily accessible, thermoregulation and activity costs were 53–58% lower and TME was 26–31% lower than in free-living chicks. The proportion of TME allocated to tissue formation (13–15% deposited as tissue plus 10–12% synthesis costs) was low in the shorebirds, and reductions in food intake may therefore sooner lead to stagnation of growth than in parent-fed chicks. Furthermore, the need to forage limits potential for saving energy by reducing activity in periods of food scarcity, because that will further decrease food intake. Self-feeding precocial chicks thus seem to operate within fairly narrow energetic margins. At the same time, self-feeding may allow birds to use food types that could not be profitably harvested if they had to be transported to the young.

NESTING ECOLOGY OF RESIDENT LOGGERHEAD SHRIKES IN SOUTHCENTRAL FLORIDA

I studied the reproductive ecology of Loggerhead Shrikes (Lanius ludovicianus) in southcentral Florida from 1991 through 1993. Pairs were sedentary and defended territories year-round. Completed nests were found from late December to mid-May. Nesting peaked during mid-March with second and third nestings attempted from late March to late May. Sixty percent of all nests were built in blackberry bushes (Rubus betulifolius), but cabbage palm (Sabal palmetto) and wax myrtle (Myrica cerifera) also were used frequently. Mean nest height was 1.6 m and mean clutch size was 4.3 eggs. A mean of 17 days was required for incubation and the mean fledging period was 15 days. Nest failure occurred more often during the incubation than the nestling stage. The majority of nest losses were due to predation and inclement weather (49 and 20 nests, respectively). Mean hatching success was 87%, and 81% of chicks fledged successfully. Nesting success (percentage of nests that fledged at least one young) was 55%, and an analysis of other studies that used this measure detected significant clinal variation in Loggerhead Shrike nesting success, with success rate positively correlated with latitude. Unlike conspecifics in northern latitudes where second broods are considered rare, 96% of breeding pairs in Florida attempted second broods.

PREFLEDGING ENERGY REQUIREMENTS IN SHOREBIRDS: ENERGETIC IMPLICATIONS OF SELF-FEEDING PRECOCIAL DEVELOPMENT

Abstract Understanding ecological consequences of avian developmental modes requires knowledge of energy requirements of chicks of different positions in the precocial–altricial spectrum, but those have rarely been measured in birds with self-feeding precocial young. We studied prefledging energy budgets in chicks of Black-tailed Godwit (Limosa limosa) and Northern Lapwing (Vanellus vanellus) in the field and in the laboratory. Lapwings show slower growth than godwits, reaching a 29% lower fledging mass (142 vs. 201 g) in a 32% longer period (33 vs. 25 days). Daily energy expenditure (DEE), measured by the doubly labelled water (DLW) technique, and daily metabolized energy (DEE plus energy deposited into tissue) increased proportionally to body mass at similar levels in both species. Total metabolized energy (TME) over the fledging period was 8,331 kJ in godwits and 6,982 kJ in lapwings, 39 and 29% higher than an allometric prediction (Weathers 1992). That suggests that self-feeding precocial chicks have ...

Old endemics and new invaders: alternative strategies of passerines for living in the Australian environment

Life history parameters of ”old endemics” and ”new invaders” among the Australian passerines were compared, controlling for phylogeny by using current, phylogenetic research methods. Old endemics were found to have significantly smaller clutches and demonstrated significantly more cooperative breeding than the new invaders, whose fledging periods are significantly longer than those of the old endemics. We argue that breeding under conditions of a small annual food increment during the breeding season, as is probably the situtation in Australia, is possible only when clutch size is small, or while breeding cooperatively, or by extending the fledging period. Our data show that the old endemics use the first two options, while the new invaders employ the third.

Attendance and Effects of Disturbance on Coastal Common Murre Colonies at Point Reyes, California

-We surveyed six Common Murre (Uria aalge) colonies in the vicinity of Elephant Seal Cove Beach (ESCB), Point Reyes National Seashore, Marin County, California from 1995 through 1997 to investigate the effects of disturbance on local murre populations in the wake of a small shipwreck and to establish seasonal and diurnal attendance patterns of coastal murre populations. Following the shipwreck in 1995, one colony (Cliff Rock West) was abandoned, and three others (Flattop Rock, Mid Rock, and East Rock) experienced reduced productivity due to disturbance and predation by Brown Pelicans (Pelecanus occidentalis), Western Gulls (Larus occidentalis), and Common Ravens (Corvus corax). A fifth colony, Face Rock, farthest from the grounding site, was apparently not affected. Murres attended Cliff Rock West only early in 1996, and not at all in 1997. A new colony formed on another seastack (Northwest Rock) after murres left the Cliff Rock West colony in 1996. However, no eggs were observed at Northwest Rock in 1996 and this colony was abandoned early in 1997. Seasonal attendance among colonies on Flattop Rock, Mid Rock, and East Rock followed a similar trend in both 1996 and 1997. Murre attendance fluctuated widely until the onset of egg-laying in early May, but then stabilized and increased somewhat untilJuly, when numbers began to drop at the end of the fledging period. Both air temperature and the upwelling index (UI) were significantly correlated with murre attendance in May and June during the incubation and nestling periods. Mean attendance increased 18-30% at these colonies between 1996 and 1997. Diurnal attendance in 1996 and 1997 varied both within and between colonies and days, yet there was a significant downward trend in numbers throughout the day, as well as an effect of colony disruption by other marine species. Given that seasonal and diurnal attendance patterns of Flattop, East, and Mid Rocks in 1996 and 1997 appear similar, both between years and to other studies, we assume that these colonies recovered quickly following the 1995 shipwreck. However, interspecific interactions and predation continue to affect diurnal attendance patterns and productivity of these colonies. Received 5 April 1998, accepted 11 October 1998, final acceptance 27 March 1999. Waterbirds 22(1): 130-139, 1999 Seasonal and diurnal attendance has been examined for a number of Common Murre populations (Lloyd 1975; Birkhead 1978a; Slater 1980; Harris et al. 1983; Hatch and Hatch 1989; Takekawa et al. 1990). During the incubation and nestling periods, the number of birds on a colony may be influenced by ambient weather; numbers may be lower during periods of high winds (Birkhead 1978a; Gaston and Nettleship 1981) or warm temperatures (Murphy and Schauer 1994). Few studies have investigated attendance patterns in relation to disturbance. Aside from human disturbance, disruption to murre colonies may be caused by predators and competitors; such effects have been recorded in studies of murre behavior, survivorship, productivity, and the costs and benefits of coloniality (Birkhead 1977; Spear 1993; Sydeman 1993; Parrish 1995; Gaston and Elliot 1996; Schauer and Murphy 1996). On 10June 1995, the vessel Wayfarer, a 42' Grand Banks pleasure-craft, ran aground ne r Elephant Seal Cove Beach, Point Reyes Headlands, Marin County, California (Fig. 1). As a result of the wreck, engine oil, debris, and approximately 200 gallons of diesel fuel were released into coastal waters (Point Reyes National Seashore Case/Incident Record #950136). During the event, a U.S. Coast Guard helicopter was dispatched to the scene to rescue the one-man crew.

Mass stranding of wedge-tailed shearwater chicks in Hawaii.

Unusual numbers of wedge-tailed shearwater (Puffinus pacificus) chicks stranded on Oahu (Hawaii, USA) in 1994. Compared to healthy wedge-tailed shearwater (WTSW) chicks, stranded chicks were underweight, dehydrated, leukopenic, lymphopenic, eosinopenic, and heterophilic; some birds were toxemic and septic. Stranded chicks also were hypoglycemic and had elevated aspartate amino transferase levels. Most chicks apparently died from emaciation, dehydration, or bacteremia. Because many birds with bacteremia also had severe necrosis of the gastrointestinal (GI) mucosa associated with bacteria, we suspect the GI tract to be the source of disseminated bacterial infection. The identity of the bacteria was not confirmed. The daily number of chicks stranded was significantly related to average wind speeds, and the mortality coincided with the fledging period for WTSW. Strong southeasterly winds were a distinguishing meteorologic factor in 1994 and contributed to the distribution of stranded chicks on Oahu. More objective data on WTSW demographics would enhance future efforts to determine predisposing causes of WTSW wrecks and their effects on seabird colonies.

A dwarf Atlantic Puffin fledgling Fratercula arctica from Nólsoy, Faeroe Islands

An unusually small Atlantic Puffin fledging Fratercula arctica was found on Nólsoy, Faeroe Islands, in August 1997. The bird was fully feathered with no down remnants and left the colony during the peak of the fledging period. Some of its measurements (those where feather length is crucial, such as wing and tail) fell within the range of minimal values found in young puffins fledging prematurely. Others, like bill and tarsus lengths with a prevailing skeletal component, were less than the lowest known values. Very small body size seems to account for the very low body mass of the bird. However, proportionally developed pectoral muscles as well as the bird's overall good appearance (fully feathered with no down) and behaviour indicated that it apparently was not food stressed or starving.

Nestling feeding strategy of the British storm‐petrel Hydrobates pelagicus in a Mediterranean colony

The pattern of chick feeding of the British storm‐petrel Hydrobates pelagicus in a Mediterranean colony was examined by weighing chicks at 24‐h intervals on different days during the nestling period. In order to calibrate daily mass increments (NET) against number of feedings, daily mass changes of chicks were regressed upon the sum of positive mass increments recorded overnight (SUM) during four nights. The average meal size delivered to chicks per night by one parent was 3.5 ß 1.3 g or 12% of adult weight. This was insufficient for sustaining constant chick mass during a day. On average 85% of chicks were fed each night, and the mean interval between feeds was 1.2 ß 0.5 nights. Nightly feeding frequencies differed among days, but this night‐to‐night variation was not related to meteorological conditions. Both food requirements necessary for chick body maintenance (zero‐growth) and meal size were relatively constant for ages up to 59 days. However, feeding frequency decreased throughout the fledging period, accounting for agespecific variation in growth rates until fledging. Food requirement and feeding patterns at Benidorm were different from North Atlantic colonies. None the less, growth patterns were almost identical, suggesting adjustment to maintain chick body mass at a determined level, as food delivery to nestling appears to be regulated to chicks’nutritional requirements.

Scramble feeding in jackass penguins: within-brood food distribution and the maintenance of sibling asymmetries

Sibling asymmetries in asynchronously hatching jackass penguin, Spheniscus demersus, broods allow more efficient resource use than in artificially synchronized broods. Behaviour that determines food allocation and maintains weight asymmetries between siblings was examined. Total time spent begging and feeding by each chick during a feeding episode was measured at seven two-chick and 43 singleton nests, with repeat observations spanning the entire fledging period. First-hatched (A) chicks either obtained more feeding time, or begged less for the same feeding time, than their siblings (B-chicks) in all but one age category (21–40 days). At this age increasing demands for food associated with rapid growth, coupled with increasing mobility, appeared to intensify competition, and A-chicks had to beg longer for the same feeding time than their siblings. By 41–60 days A-chicks were again gaining more feeding time than B-chicks. A-chicks were better coordinated, using their weight advantage effectively during scramble feeding. A- and B-chicks generally spent more time begging for a given amount of feeding time than did singletons. A-chicks fed more at the beginning than at the end of a feeding episode, while B-chick feeding rate remained the same, suggesting a drop in A-chick feeding rate due to satiation, which may prevent asymmetries from becoming too large. In this way A-chicks maintain their weight and competitive advantage, without risking B-chick starvation when food supplies are adequate for both siblings.

The Breeding Biology of the Lesser Noddy on Pelsaert Island, Western Australia

SummaryThe Lesser Noddy Anous tenuirostris (melanops) is a small, dark-plumaged, tropical tern which breeds only on three islands in the Houtman Abrolhos, off Western Australia, where it nests in mangrove trees. On Pelsaert Island, in 1991, the single egg clutches were laid over a 102day period from late August to early December, peaking in September. The incubation period averaged 34 days and the fledging period 40 days. Overall, 60% of eggs hatched and 47% gave rise to free-flying young. Storms caused extensive egg loss from the more exposed nests; some pairs laid replacement eggs. Birds laying earlier in the season tended to use more sheltered sites and, consequently, had a higher reproductive success than those laying later and in more exposed areas.