Influence of weather on reproductive success of northern fulmars in the Canadian high Arctic

The northern fulmar (Fulmarus glacialis) is a common seabird of the North Atlantic Ocean, with breeding colonies broadly dispersed between 45°N and 80°N. At higher latitudes, breeding fulmars experience extensive sea-ice and presumably snow and low temperatures which do not affect fulmars in the southern part of the breeding range. We studied the relationship between weather and reproductive success of northern fulmars breeding at two colonies in the Canadian high Arctic. Collectively, hatching success, fledging success, and productivity (chicks fledged per egg laid) were similar between our study and results from colonies located south of the Arctic. However, a larger proportion of fulmars at apparently occupied sites (AOS) in high Arctic colonies appeared to forego egg-laying, resulting in lower proportions of chicks fledged per AOS. Extreme inclement weather was the major factor influencing nesting success, resulting in pulses of egg or chick loss during or immediately following major storms, although the mechanism of effects appeared to differ between the two colonies. For Arctic fulmars, the risks of nest failure due to stochastic, deleterious weather events may be offset by the predictable abundance of food supplies during chick-rearing in Arctic waters.     

Breeding performance of Indian Sarus Crane Grus antigone antigone in the paddy crop agroecosystem

The breeding performance of the Indian Sarus Crane Grusantigone antigone Linn. was studied in the agriculturallandscape of Gujarat, India during 1996. Detailed records of a total of22 nests were compiled from egg-laying till fledging. Eleven clutches(50.0%) produced at least one chick. Ten clutches (45.45%) weredestroyed due to various mortality factors, and one clutch (4.50%)failed to hatch. Of the 10 pairs whose clutches were destroyed, at leastfour renested. Renesting in the wild was reported for the first time.Egg destruction was mainly due to flooding (12.20%), predation (21.95%)and conflicts with farmers (14.64%). Predation accounted for 31.58% ofchick mortality. The egg and chick mortality factors identified wereunique to the agricultural ecosystem. The number of chicks that hatched andof chicks fledged per nest did not differ significantly in differentmicrohabitats. Hatching success was higher in non-cultivableagricultural marshland (68.18%) compared to paddy cultivated marshland(38.48%), mainly due to human disturbance and higher predation risk.Overall breeding success was 19.51%. Juveniles comprised only 8.96% ofthe total number of Sarus Cranes sighted during the post-breedingperiod. One of the causes of poor breeding performance in theagricultural landscape was increasing conflict with the farmers, whosuffer economic loss due to nesting in the crop field. If compensated,farmers may help in Sarus Crane conservation efforts.     

Keeping it regular: Development of thermoregulation in four tropical seabird species

The thermoregulatory capacity of a species can determine which climatic niche it occupies. Its development in avian chicks is influenced by numerous factors. Furthermore, it is suggested that altricial chicks develop their thermoregulatory capacity post-hatching, while precocial chicks develop aspects of this in the egg. We investigated the development of thermoregulation of four co-occurring seabird species in the Seychelles; namely white, ground-nesting white-tailed tropicbirds (Phaethon lepturus) and tree-nesting fairy terns (Gygis alba); and dark plumaged, tree-nesting lesser noddies (Anous tenuirostris) and ground- and tree-nesting brown noddies (A. stolidus). White-tailed tropicbirds have semi-altricial chicks, while the remaining species have semi-precocial chicks. Cloacal temperatures (T_b) were measured at five day intervals from newly hatched chicks and compared over time, and with adult T_bs. Initial T_bs of all chicks, except fairy terns, were lower than those taken when chicks were older. Brooding cessation generally coincided with feather development, as did an increase in T_b. Mean chick T_b was significantly lower than mean adult T_b for all species, but only white-tailed tropicbird and brown noddy chicks in tree nests differed significantly from mean adult T_b when chick T_b at five day intervals were considered. There was a significant interactive effect of nest site and age on brown noddy chick T_b, but chick colour did not have a significant effect on T_b. However, brown noddy chicks on dune crests maintained a constant T_b sooner than chicks in tree nests. Our results demonstrate that tropical seabird species have a more delayed onset of thermoregulatory capabilities when compared with those in temperate environments, perhaps as nest sites are less thermally challenging. Nest microhabitats and behavioural thermoregulation, are likely more important during early chick development for these species.     

Assessment of territory quality and its effects on breeding success in a migrant passerine, the Wheatear Oenanthe oenanthe

This paper examines how a returning migrant assesses the quality of an area as a breeding territory before the period of peak food demand and how effective the assessment is in terms of breeding success. Male Wheatears Oenanthe oenanthe return from Africa to choose territories in the Breckland of eastern England about March, females arriving shortly after males. The food supply was predictable: prey densities during the breeding period (egg-laying to chick independence) were strongly correlated with prey densities at the same sites during the period of arrival and territory establishment. Prey densities were also related to vegetation structure, averaging highest on short turf. Male arrival date and territory size were not significantly related to prey density but were strongly related to vegetation structure, implying that birds used vegetation as an indirect clue to prey availability. Neither territory size nor nest spacing appeared to affect nest losses caused by predators. The major variations in number of young fledged (other than predation) were caused by the number of nestlings hatched and presence of a second brood. Both early arrival and an early first brood improved first-brood success and were necessary for a second brood. Not all birds which arrived early bred early enough for a second brood. First-brood hatching date was strongly negatively correlated with pre-breeding prey availability but not significantly related to vegetation structure. Thus by using vegetation as a clue to habitat quality, some pairs suffered reduced breeding success. This result implies that birds may not be able adequately to assess prey density directly at the time of territory establishment. The critical period for food availability may not be the period of peak demand (nestling period), when food is relatively abundant, but is probably the pre-breeding period when females must accumulate reserves for eggs and when the food supply is poor. Food supply during this period may determine the timing of breeding and the ability to rear a second brood, and may thus have a greater effect on breeding success.     

Annual variation in breeding biology of gentoo penguins, Pygoscelis papua, at Bird Island, South Georgia

The breeding biology of the gentoo penguin, Pygoscelis papua , was studied over a three-year period (1986–1988) at Bird Island, South Georgia, with particular reference to birds of known age or breeding experience. Laying date varied significantly between all three years, being three weeks later in 1987, when the breeding population decreased markedly. Factors involved in the timing of breeding are discussed. Within years egg-laying was highly synchronous: 95% of clutches were initiated in 14·5 days or less. The incubation period was 35 days and the laying interval, between the two eggs, 3·3–3·4 days. Chicks creched when 25–30 days old, and this varied between years, possibly related to food supply and chick growth. Chicks left the colony for the first time between 75 and 85 days of age. The breeding population at Bird Island decreased by 20% and increased by 84% in successive years during the study period. Breeding success (chicks fledged per egg laid) varied between 0·33 and 0·65 within colonies, but for the whole island was very consistent over the three years: 0·45, 0·51 and 0·47. Overall, colony differences were not correlated between years. Disturbance from Antarctic fur seals, Arctocephalus gazella , is suggested as the cause of consistently lower breeding success at one colony. Mean egg weight varied annually, and with age of the breeding bird, nest location and, in one year, with laying date. Young, first-time breeders laid smaller eggs and had lower breeding success compared to older, experienced birds, similar to other seabirds. However, they differed from other species in laying on average earlier than older birds. The relationship between age, egg weight, laying date and breeding success is discussed in relation to predation and seasonal food supply.     

Maternal nutrition, egg quality and breeding success of Scottish Ptarmigan Lagopus mutus

Samples of Ptarmigan eggs were hatched in captivity. They had been taken from ground adjacent to study areas where the wild birds' breeding success by early August, and their food plants, were measured.
Almost all deaths of chicks in captivity occurred within a few days of hatching and examination postmortem showed no specific cause. The proportion of chicks which died in captivity before 15 days of age varied markedly between years and study areas. These variations occurred in parallel with variations in breeding success in the wild populations from which the eggs had been taken. It was concluded that the survival of chicks both in captivity and in the wild was determined in part before the eggs hatched.
Variations in breeding success from year to year were correlated with the number of days that the food plants had been growing before the hens finished laying. Breeding success in the wild and chick survival in captivity were better for a 'rich' area overlying some base-rich rocks than for a 'poor' one overlying granite and with less blaeberry. It was inferred that, as in Red Grouse, maternal nutrition affected breeding success through the quality of the eggs.     

Seasonal variation in reproductive measures of tropical Roseate Terns Sterna dougallih previously undescribed breeding patterns in a seabird

Seasonal variation in egg-laying, egg size, hatching success, hatchling mass, fledging success and chick growth of Roseate Terms Sterna dougallii breeding on Aride Island (Seychelles), Indian Ocean, were studied in 1997 and 1998. I investigated to what extent two patterns, common in a range of species, were followed by tropical Roseate Terns: (a) seasonal decrease in clutch size, egg size and breeding success and (b) an increase in breeding success with increasing egg weight. In 1997 (a poor year), the earliest nesting birds laid significantly smaller eggs, and chicks were lighter at hatching than those of peak nesting birds. The mean clutch size, of 1.04 eggs, showed no seasonal variation and no 'b'-eggs hatched. In 1998 (a good year) the earliest nesting birds laid eggs of similar size and their chicks were of similar weight to those of peak nesting birds. Mean clutch size, of 1.25 eggs, increased significantly through the season and about 60% of the 'b'-eggs hatched. In 1997, hatching success was 57% whereas in 1998 it was 80%. In both years, breeding success declined significantly through the season. The fact that the earliest breeding birds laid smaller eggs in a poor year and smaller clutches in a good year is in marked contrast to a range of other species, and to temperate-nesting Roseate Terns. Egg volume explained about half of the variance in hatchling mass in both years, but only 15% of the variation in linear growth rate. Hatching date was the only variable with a significant effect on fledging success. Roseate Terns on Aride seemed to sacrifice egg size and clutch size for earliness of laying. Presumably it is a strategy of older birds to lay as early as possible and may be regarded as a response of tropical Roseate Terns to breeding under relatively poor, and seasonally declining, food conditions.     

The breeding biology and causes of nest failure of Scottish Black-throated Divers Gavia arctica

The breeding biology and causes of nest failure were examined for Black-throated Divers Gavia arctica in core areas of their Scottish breeding range in 1983–1987. Breeding was confirmed for up to 88% of territorial pairs each year ( n = 28–62), and 76% of nests were on islands. Hatching success was consistently low with, on average, only 43% of territorial pairs managing to hatch a clutch each year; 64% of recorded nest failures occurred during the first week of the 4-week incubation period.
Overall breeding success in West Sutherland in 1984–1987 averaged 0.23 chicks per territorial pair per year, while in Ross-shire for 1986–1987 it was 0.29. Forty percent of hatched chicks survived to fledge, and 92% of recorded deaths occurred in the first fortnight after hatching; 4.8% of fledged broods held two chicks.
Causes of nest failure were assessed with the aid of surveillance cameras. Approximately 30% of losses were due to water level changes (mostly floods), 48% to predators (primarily nocturnal mammals, but also Hooded Crows Corvus corone ), 13% to human egg collectors and 5% to desertion following human disturbance.
Scottish Black-throated Divers produce only half the number of chicks tentatively estimated to be required to maintain a stable population. The main difference between the Scottish and more successful Swedish populations is in the degree of chick mortality.     

Survival analysis of Little Penguin Eudyptula minor chicks on Motuara Island, New Zealand

Chick survival of Little Penguins Eudyptula minor was studied on predator-free Motuara Island, Cook Strait, New Zealand (41̀05'S, 174̀15'E), in 1995 and 1996. We used the Kaplan-Meier estimator and robust Cox regression to estimate chick survival rate (pL se) at 0.325 pL 0.044, leading to an estimated survival from laying to fledging of 0.13 or a reproductive output of 0.26 chicks per pair and breeding attempt. Starvation posed the greatest mortality risk, followed by unknown factors and rain. Risk of death due to rain was restricted to the guard stage, whereas starvation occurred throughout the nesting period, though with a peak in the early guard stage. Significant seasonal differences in survival rate were detected in both years, but with reversed trends, survival decreasing with the season in 1995 and increasing in 1996. Failure of adults to relieve their partner on the nest after chicks hatched accounted for 16% mortality or 34% of all chick deaths. Differences in chick survival rate between nest types were significant in 1995, a year with high rainfall, but not in 1996. Nests in the base of hollow trees had the highest chick survival rate. Of chicks in open nests - a nest type that is unusual for this species - 5.4% fledged. Our results suggest that on Motuara Island good breeding sites are scarce and that the food supply has been poor during the years of this study.     

Effects of clutch size and egg-laying order on the breeding success in the Little Tern Sterna albifrons on the Nakdong Estuary, Republic of Korea

Survivorship of Little Tern Sterna albifrons eggs and chicks was followed on an islet in the Nakdong Estuary, Republic of Korea, in 1995 and 1996. Mean egg size and incubation period were significantly different between the 2 years. The maximum clutch size was three eggs, and the second egg in the clutch often hatched earlier than the first, while most of the third eggs hatched last. In 1996, when the fate of 249 eggs from 106 nests was followed for 40 days, hatching success, fledging success and breeding success were 77%, 40% and 31%, respectively. High mortality occurred in the early chick stage, mostly because of rain and predation by Weasels Mustela sibirica. The breeding success per egg was 14% in one-egg clutches, 28% in two-egg clutches and 34% in three-egg clutches. This difference was mainly attributed to the lower hatching success in the smaller clutches. In three-egg clutches, the third egg showed significantly lower breeding success than siblings. The main foods of the Little Tern were Tridentiger obscurus, Engraulis japonicus, Hyporhamphus intermedius, Acanthogobius flavimanus (all fish), Palaemon sp. and Crangon affinis (shrimps). The feeding frequency was, apparently, not affected by time of day and age of chicks but was probably influenced by weather conditions. Newly hatched chicks failed to eat 25% of the prey brought to them, although this decreased with the age of the chicks.     

FACTORS AFFECTING BREEDING OF RAZORBILLS ALCA TORDA ON SKOKHOLM

A study of the breeding biology of the Razorbill was carried out on Skokholm (South Wales) during 1971-73. Birds ringed or colour ringed before the study began provided additional information upon the effects of age on breeding. Mean laying date was delayed in 1972, compared with 1971; the effect is attributed chiefly to stormy weather which upset colony attendance. Eggs were also smaller in 1972. A seasonal decline in egg size (volume) was noted in all three years, attributed mainly to the later laying of young birds. Egg size increased with age, at least up to the fifteenth year. Eggs lost totalled 30% of those laid; 73% of this total was due to predation by Herring Gulls and of Jackdaws. Most losses (45%) occurred during the first 10 days after laying. Of lost eggs, 25% were replaced, usually 14 days after the loss of the original; only eggs laid and lost early in the season could be replaced. Only 7% of the chicks which hatched failed to fledge. Most (62.5%) chick losses occurred in the first week of nestling life, when chick weight was related to egg size. Afterwards, both growth rate and fledging weight were independent of egg size. The chicks fledging early in the season were heavier than later chicks. Failure to fledge was mainly due to a breakdown in behaviour between parent and young, rather than to predation. Breeding success was highest for birds breeding early in the season, most of which were older, more experienced breeders. These laid early enough to replace an egg if it was lost; they produced large eggs, and their chicks were therefore both heavier than average during the critical first 7–10 days of life, and fledged at a high weight. Thus experience accumulated with age, and the ability to lay early in the season are important for successful breeding in the Razorbill.     

Brood reduction in the Blue-eyed Shag Phalacrocorax atriceps

Brood reduction is common in a population of Blue-eyed Shags on Signy Island, South Orkney Islands. This paper describes possible adaptations which may reduce the brood. In clutches of three, the last egg was smaller, and hatched 2.4 days later than its siblings. Whilst 78–84% of first and second ('A' & 'B') chicks fledged, only 11 % of 'C' chicks did. In a sample of artificially synchronized broods chick survival was as high as in normal asynchronously hatching broods, but there were more cases of total brood loss. The age at which the C chick died was related inversely to the length of the A-C hatching interval. Relative differences in sibling weights were highest during the first 12 days, when most of the C chick deaths occurred. At this age the daily food requirements of each brood of three was one-tenth that of each brood of two just prior to fledging. It is suggested that C chicks were unable to compete effectively for a food supply which was limited by the parents, rather than by the environment. The asymptotic weight attained by A chicks was inversely related to brood size, and was greater than that of B or C chicks. Normal asynchronous broods produced at least one heavy (A) chick and one medium weight (B) chick, whilst in synchronized broods the asymptotic weight attained was similar to that of B chicks in normal broods.     

Chick loss in the Falkland Skua Catharacta skua antarctica

Data on reproductive success of 110 Falkland Skua Catharacta skua antarctica pairs were gathered during the austral summers of 1988–1989 and 1990–1991 on New Island, Falkland Islands. Adults laid two eggs 2–3 days apart and began incubation with the first egg. For the years combined, 1.39 chicks per nest hatched and 0.84 chicks per nest fledged (fledging was defined as surviving to 16 days of age). Brood reduction was common; 43% of the two-chick broods were reduced to one, and mortality was concentrated on the younger chick. Although asynchronous hatching and differential death are consistent with Lack's brood reduction hypothesis, application of O'Connor's quantitative criterion revealed that sibling competition may not be responsible for the observed chick mortality. Furthermore, because no aggressive interactions between chicks were observed or detected indirectly, siblicide may be absent in this population. Instead, predation modified by a variety of factors may have led to the greater mortality of the second-hatched chick.     

Influences of adult age and experience, nest location, clutch size and laying sequence on the breeding success of the Great skua Catharacta skua

In 881 nesting attempts by Great skuas on Foula during 1975 and 1976, 1.24 chicks were fledged per pair. Addled eggs and egg predation were the main causes of losses. Eggs rolled out of the nest were not retrieved. Almost all chicks which hatched also fledged. Young or inexperienced breeders were almost as successful as older or experienced pairs. Birds producing single egg clutches and addled eggs usually also showed low aggression and held small territories. Egg predation was greatest at high nest density, when food availability was low, and when adult aggression score was low. High density nesting seems to have been imposed by the limited size of the island and prolonged population increase.     

Climate fluctuation effects on breeding of blue penguins (Eudyptula minor)

Abstract

El Niño and La Niña climate perturbations alter sea currents and food availability for seabirds in many areas of the world. This changes their breeding success and mortality. Blue penguin (Eudyptula minor) breeding success is dependent upon whether one or two clutches per season are laid, and the hatching and fledging success of these clutches. This study uses six years of data from five blue penguin breeding colonies, three from Taiaroa Head, Otago Peninsula and two from Oamaru, to examine whether annual variation in breeding success correlates with El Niño/La Niña perturbations. When La Niña conditions prevailed, penguins started breeding later, and there was a lower proportion of double breeders than in El Niño and normal years. The probability of a newly hatched chick surviving to fledging was also dependent on whether large‐scale climatic conditions prevailed, whereas hatching success and overall breeding success (number of fledged chicks per breeding pair) showed no correlation with climate perturbations.     

Testing the relationship between clutch size and brood size in the Coot (Fulica atra)

The time between egg laying and chick fledging is of crucial importance for the survival of young birds. I analyzed breeding output at consecutive phases of growth of young Coots (Fulica atra) relative to the clutch size and laying date. Considering the specific breeding biology of the Coot, I tested whether chick survival reveals clutch size-dependent variability. Clutch size did not affect hatching success; it only affected brood size, and that merely temporarily. During the first 20 days after hatching, i.e. during the time of the highest chick mortality, birds with larger clutches lost chicks at a higher rate. As a result, the number of fledged chicks was independent of the initial number of chicks, and pairs with different clutch sizes had a similar number of fledglings. The laying date had no effect. This pattern of age-related chick survival points to the greater role of the type of chick growth (semi-precocial) and behavior in their survival.     

Experimental evidence for the relationship between food supply, parental effort and chick survival in the Lesser Black-backed Gull Larus fuscus

We studied breeding success, chick growth, parental effort and chick behaviour in two groups of Lesser Black-backed Gulls Larus fuscus whose chicks were provided with additional food until 7 days after hatching or until fledging. These data were compared with those from control pairs which we studied simultaneously to test the hypotheses that food was in short supply during the chick stage at the colony site and that in such circumstances the behaviour of adults and young is mainly responsible for the low success. Pairs whose chicks were fed with additional food until fledging showed a higher fledging success than control pairs (intermediate for pairs of first experimental group). During the first week after hatching, experimental adults of both groups were present together at the territory for longer than control pairs. In adult females of experimental pairs, the length of feeding trips was shorter than in females of control pairs, whilst the rate of chick feeding was more frequent in the experimental broods. After the chicks were 7 days old, differences were significant only for the experimental pairs whose chicks were provided with additional food until fledging. Chicks fed until fledging showed a higher daily mass and wing-length increments and reached a higher fledging mass at an earlier age than both control chicks and chicks which were provided with additional food until day 7. Starvation occurred only in control chicks and in chicks of the first experimental group after we had stopped providing food. When food was in short supply, fledging success of gulls was adversely affected as a result of both starvation (because of the lower feeding rates of chicks) and a higher predation rate (arising from changes in behaviour of both adults and chicks).     

Costs of large communal clutches for male and female Greater Rheas Rhea americana

The breeding system of the Greater Rhea Rhea americana is almost unique among birds as it combines harem polygyny and sequential polyandry, with communal egg-laying and uniparental male care. In this species, large communal clutches (more than 30 eggs) are rare and have a lower hatching success than smaller clutches. Here we analyse the proximate causes of hatching failures and the costs of large communal clutches (and therefore the costs of extensive polygyny) for males and females. We evaluated if length of the nesting period, egg viability, egg losses during incubation and male parental activity at the nest were affected by clutch size. We also evaluated if chicks hatched from large clutches have a lower survival during the first 2 months after hatching. Large clutches had longer nesting period and lower hatching success, mainly as a result of bacterial contamination of the eggs and increased hatching asynchrony. In addition, large clutches tended to lose more eggs as a result of accidental breakage or predation. Male activity at the nest and chick survival were not related to clutch size. Low hatching success, nest predation risk and energetic costs associated with large clutches penalize females that join large harems and males that accept additional eggs into the nest.     

Effects of individual life-history traits and weather on reproductive output of Black-headed Gulls Larus ridibundus breeding in the Wadden Sea, 1991–97

Capsule Annual breeding success was relatively constant and is shown to be related to clutch size and growth rate and to be positively affected by rain during egg-laying and advanced chick-rearing phase.

Aims To provide the first long-term data on breeding success of Black-headed Gulls in the Wadden Sea, to analyse its intrinsic and environmental co-variates, and to re-assess the significance of the severe winter 1995/96 on reproduction.

MethodsIn a relatively small colony at the Wadden Sea coast, clutches were selected randomly and enclosed to determine clutch size, egg biometrics, hatching and breeding success, and chick development in 1991 and from 1994 to 1997. Weather data (temperature, rain, wind) were related to life-history traits (clutch size, egg volume, chick development) and reproductive success.

Results Mean annual breeding success was 0.7 fledglings per pair. In 1996, breeding success tended to be lower and chick growth rate was significantly lower. Hatching success was lower in small clutches, chick mortality increased with decreasing chick growth rate. Rain during the egg-laying phase increased clutch size and decreased clutch predation. Rain during the early post-natal phase impaired chick growth. Rain during the phase of linear growth affected chick growth and fledging success positively and brood predation negatively.

Conclusions Breeding success of Black-headed Gulls breeding in the Wadden Sea is relatively constant between years, probably due to the use of terrestrial and marine feeding habitats. Rain may increase the availability of intertidal and terrestrial prey and thus may affect time budgets and food provisioning of parents positively. Lower breeding success in 1996 might have been caused by a relatively dry breeding season and possibly by the preceding severe winter.     

The importance of observer effort on the accuracy of breeding success estimates in the Common Guillemot Uria aalge

ABSTRACT

Capsule: A data-thinning approach was used to assess the effects of reducing the frequency of nest-checks on estimates of breeding success of Common Guillemots Uria aalge. Inter-year and inter-colony differences in fledging age and their implications for setting a minimum age after which a chick could be assumed to have fledged were evaluated.

Aims: To assess the consequences of reducing sampling frequency on the estimation of breeding success, and on the robustness of the assumption that breeding has been successful if a chick survives to 15 days old.

Methods: Breeding success, ages at fledging and loss of chicks were estimated from daily checks at two Scottish colonies over a six-year period. Data-thinning was used to assess the consequences of reducing checks from daily to every two or three days. Breeding success was recalculated assuming that all chicks surviving to 15 days fledged.

Results: Reducing the frequency of checks from daily to every second or third day resulted in a small but statistically significant increase in the estimate of success. Between 20% and 25% of chick losses occurred when chicks were ≥15 days old. Assuming that these chicks had fledged resulted in significant increases in breeding success.

Conclusion: Assumptions about whether or not a chick fledged had a greater impact on the estimate of breeding success than reducing the frequency of nest-checks from daily to every second or third day. There was no threshold age after which a chick could be assumed to have fledged. These findings are relevant to other monitoring schemes where there is pressure to reduce input. Sampling methods used in monitoring schemes need to be clearly stated and changes in protocols documented so that sampling effects can be incorporated into future analyses.