Use of novel nest boxes by carmine bee‐eaters (Merops nubicus) in captivity

Carmine bee‐eaters make attractive additions to zoo aviaries but breeding programs have had challenges and limited success. The objectives of this study were to document nesting behavior of Carmine bee‐eaters in a captive setting and compare reproductive success between a novel nest box (plastic, 17 × 30 × 22 cm) and a PVC pipe model used previously (30 cm long, 8 cm in diameter). Three bee‐eater pairs were given access to seven nest chambers (six novel boxes, one PVC model). Behavioral observations occurred during a 15‐min period in the morning or afternoon before egg production and continued until chicks fledged for a total of 87 observation periods (21.75 hr). All occurrences by an individual bird entering or exiting a nest tunnel, food provision, and the time (min) spent inside a nest cavity were documented. Additionally, daily temperature within each nest chamber was recorded. Before eggs were produced the average daily temperature (23.02°C) within the nest chambers did not differ, suggesting that nest cavity choice was not influenced by temperature. No differences were detected among pairs in percent of observed time spent inside their nest cavities or number of times a nest tunnel was entered during the incubation or fledging periods. During incubation females spent a greater percent of observed time inside the nest cavity than males (P=0.02). During the fledging period food provision did not differ between the pairs, however males entered their nest tunnels more often per hour than females (P=0.03), and males tended to provide food more often than females (P=0.053). Two pairs nested in novel nest boxes and successfully fledged one chick each. The pair that nested in the PVC model did not fledge a chick. A nest box that aids in keeping eggs intact is essential for breeding bee‐eaters in captivity, and maintaining captive populations will provide opportunities for zoo visitors to enjoy these birds and will reduce the need to remove birds from the wild. Zoo Biol 0:1–13, 2007. © 2007 Wiley‐Liss, Inc.     

Incubation feeding by male Scarlet Tanagers: a mate removal experiment

ABSTRACT Incubation feeding, where males feed their mates, is a common behavior in birds and may improve female condition, nest attentiveness, and nesting success. We used behavioral observations and a temporary mate removal experiment to test the female nutrition hypothesis for incubation feeding by male Scarlet Tanagers (Piranga olivacea). All males (N= 20) were observed incubation feeding and fed females both at the nest (x? 1.36 trips/h) and away from the nest (x? 20.1 trips/h). Male feeding rate off‐nest was negatively correlated with the duration of female foraging bouts and positively correlated with the total time females spent incubating per hour. Eggs were predated at seven of 19 (37%) nests, but nest survival during incubation was not related to either female incubation behavior or male feeding rate. During temporary removal experiments (N= 12), female Scarlet Tanagers remained on the nest significantly longer and did not have longer foraging bouts. An unexpected outcome of the removal experiments was a dramatic change in female vocal behavior. All 12 experimental females gave chik‐burr calls during the male‐removal experiments (x? bout length = 11.7 min), but during normal observation periods only six of 20 females at the incubation stage gave chik‐burr calls (x? bout length = 0.7 min, N= 20). Our results suggest that female tanagers likely gain nutritional benefits from incubation feeding, but male feeding may not improve immediate reproductive success. Nine of 54 (17%) nestlings in five of 17 broods (29%) were extra‐pair young (EPY), indicating that males could potentially benefit from incubation feeding via mate retention and fidelity as well as, or instead of, through immediate gains in reproductive success. Our study indicates that females benefit from incubation feeding and do not simply passively accept food from their mates, but instead may influence male feeding rates through direct (e.g., mate following and vocalizing) and indirect (the threat of mate abandonment or cuckoldry) means.     

Nest Predation Avoidance: an Alternative Explanation for Male Incubation in Acrocephalus melanopogon

In the monogamous moustached warbler, male incubation changes from predictably variable (it is dependent on ambient temperature and time of day in April) to high average levels across the day (with no predictor variables in May) as the season progresses. In contrast, females contribute the constant incubation component from April to May. This paper investigates possible explanations for the change in male incubation effort involving changing risks to either (1) embryonic survival within the egg, and/or (2) egg predation. Using egg temperature readouts, the probability of reaching the 25 °C thermal threshold (below which embryonic development ceases) across the season against the probability of predator sightings 0–15 m from the nest was calculated. The results show an inverse relationship between these two risks. During April, male incubation correlates with egg cold stress and changeovers between males and females occur prior to egg cooling below the thermal stress line. During May, the risk of predation increases. The results show increased predator encounter rates from April to May and active nest defense by the incubating parent. Furthermore, high male incubation reduces brood predation. Selection for reduction of the costs of laying replacement clutches (after predation) is suggested given high male incubation and infrequent male-female changeovers during midday, when egg temperatures are highest, with direct benefits to females of increased foraging. Thus, the shift in male incubation across the season may be explained by minimization of changing risk to offspring survival.     

A new method for catching cavity‐nesting birds during egg laying and incubation

ABSTRACT The physiological condition of female birds during the egg‐laying and incubation periods is of considerable interest and yet is relatively understudied in wild birds, primarily due to the difficulty of catching birds during this period without causing nest desertion. We therefore developed a box‐net to capture cavity‐nesting birds using sections of a mist‐net placed around a metal cubic frame. We captured female Great Tits (Parus major) as they left nest boxes during the egg‐laying and incubation periods and measured desertion rates. Using box‐nets, we captured 108 of 119 (90%) females during egg laying and 10 of 12 (83%) during incubation. Our recapture rate over two consecutive days during incubation was 50% (5 of 10). Females not captured left nest boxes before we attempted to capture them, escaped through a hole in the mist‐net, or remained in nest boxes for more than 2 h, after which we ended capture attempts. Overall, 22% of egg‐laying females deserted, with desertion rates highest early in the egg‐laying period. Desertion rates of females captured using box‐nets did not differ from those of undisturbed females. One of 10 females captured in a box‐net deserted during the incubation period. Box‐nets are portable, can be set up and taken down quickly and easily, and could potentially be used with nest boxes or natural cavities at any height. Box‐nets are easy to construct and adaptable for use with an array of cavity‐nesting birds, and can be an important tool for studying female physiology during egg laying and incubation.     

Interactive vocal communication at the nest by parent Great Tits Parus major

Although most bird species show monogamous pair bonds and bi‐parental care, little is known of how mated birds coordinate their activities. Whether or not partners communicate with each other to adjust their behaviour remains an open question. During incubation and the first days after hatching, one parent – generally the female – stays in the nest for extended periods, and might depend on acoustic communication to exchange information with its mate outside. The Great Tit Parus major is an interesting study system to investigate intra‐pair communication at the nest because males address songs to their mate while she is in the nest cavity, and females answer the male from the cavity with calls. However, the function of this communication remains unknown. In this study, we recorded the vocalizations and observed the resulting behaviour of Great Tit pairs around the nest at different breeding stages (laying, incubation and chick‐rearing). We observed vocal exchanges (vocalization bouts, alternated on the same tempo, between the female inside the nest and her male outside) in three contexts with different outcomes: (1) the female left the nest, (2) the male entered the box with food, and the female then used specific call types, (3) mates stopped calling but did not leave or enter the nest. The structure of vocal exchanges was globally stable between contexts, but females used calls with an up‐shifted spectrum during exchanges, at the end of which they left the nest or the male entered the nest. Birds vocalized more and at higher tempo during exchanges that ended up in feeding inside the nest. Birds also vocalized more during exchanges taking place during laying – a period of active mate guarding – than during incubation. We conclude that vocal exchanges could signal the females’ need for food and the males’ mate guarding behaviour, and discuss other possible functions of this communication.     

A male destroying an egg in a cooperative breeding attempt in Lesser Spotted Woodpecker Dendrocopos minor

A cooperative breeding case was found in Lesser Spotted Woodpecker (LSW) in which a male and three different females were involved. The contributions of each member of the cooperative breeding team were quantified during nest excavation and incubation. This is the first such report on LSW. During daytime, the nest was mainly occupied by the male during the final excavation phase, nest guarding, and egg laying. Aggressive interactions were recorded between two of the females during nest excavation, egg laying and incubation. The male was recorded destroying an egg presumably laid by the dominant female. The highest contribution during daytime incubation was made by the dominant female (39%), followed by the male (34%) and then by a second female (27%). The third female contributed very little at any stage. A picture of the male removing the egg was analyzed to estimate the egg maximum width, ruling out a possible runt egg. Motivations behind the behaviour of the male destroying the egg remain unclear.     

Serum prolactin and testosterone levels in captive and wild brown kiwi (Apteryx mantelli) during the prebreeding,breeding, and incubation periods

In brown kiwi (Apteryx mantelli), the male is the primary incubator, a trait that is relatively rare among birds. The maintenance of avian incubation behavior is controlled by the protein hormone prolactin (PRL). Although steroid hormone concentrations in both wild and captive kiwi have previously been reported, this study is the first to report levels of PRL in captive and wild male and female kiwi through the prebreeding and breeding seasons, and to directly compare testosterone (T) concentrations between captive and wild males during the breeding and incubation periods. Female PRL concentrations increased at the time of oviposition, whereas male PRL concentrations rose gradually between the prebreeding and incubation periods. Although males are considered the main incubator, an increase in PRL levels could help females maintain behaviors such as nest guarding, or to take over incubation the event of mate loss. A gradual increase in PRL allows the male to be ready for incubation during the long breeding season. Interestingly, T concentrations in captive males did not decrease during incubation and was significantly higher than in wild males. Continual elevated T could have an impact on sperm production through negative feedback, thereby contributing to the low egg fertility seen in captive kiwi. Therefore, determining the underlying reason for the differences in hormone levels could be significant, if not vital, for improving the success of captive kiwi breeding programs.     

Fitness consequences of male provisioning of incubating females in a desert passerine bird

Male provisioning of incubating females can increase reproductive success by maintaining physiological condition of females and consistency of incubation. The effects of male provisioning on the maintenance of incubation temperature and embryo development should be particularly pronounced in environments where ambient temperature exceeds the tolerance of unincubated eggs and where consistency of female incubation might be particularly important for hatching success. Here, we investigated the reproductive consequences of incubation feeding in a desert population of House Finches (Carpodacus mexicanus) in southwestern Arizona. We found that greater nest attentiveness by females was related to higher minimum incubation nest temperature, that in turn was closely associated with hatching success. Only 44% of males regularly provisioned their incubating females. Although provisioned females maintained higher incubation temperature and took fewer incubation breaks than non-provisioned females, overall, male provisioning did not influence incubation dynamics or hatching success. Further, a male’s incubation feeding rate did not correlate with male provisioning of nestlings. These results corroborate the finding that, in male House Finches, neither provisioning of incubating females nor pre-incubation courtship feeding are associated with increases in circulating pituitary prolactin––the hormone regulating male provisioning of nestlings. We suggest that incubation provisioning by male might be a component of pair maintenance behavior and that variation in male incubation behavior is best understood in relation to asymmetries in residual reproductive values between the mates.     

SOME NOTES ON THE CAPE GANNET,Morus capensis

Tarboton, W. R. 1978. Breeding of the Little Banded Goshawk. Ostrich 49:132-143.

The behaviour and vocalizations of a pair of Little Banded Goshawks Accipiter badius during part of their breeding cycle is described. Both sexes built the nest. Two eggs were laid three days apart. The first egg was incubated for 52% of the day, but this increased to 90% when the clutch was complete, of which the female's share was 86% and the male's 4%. The second egg hatched after 29 days, 18 h. The female did not hunt during the incubation or early nestling period and was fed by the male who brought her, on average, 7,0 food objects per day. Lizards formed 73% of the 91 identified prey objects, and small birds, 24%. The female and chick, when 16 days old, were killed by a predator on the nest at night.     

Breeding orange-winged Amazon parrots in captivity

Captive propagation of parrots for the companion bird trade provides a potential means of reducing the economic incentive to capture these birds from the wild. To test whether environmental and social manipulations might stimulate reproduction in captive, wild-caught orange-winged Amazon parrots (Amazona amazonica), we compared reproductive performance in pairs presented with nest boxes (controls) or nest boxes plus additional environmental and social manipulations (enriched group) consisting of misting, fruit supplementation, nest hole restriction, enlarged nest boxes, and pair separation/reunification. In the first breeding trial, in 1990, enriched pairs were more likely to lay eggs (six of seven enriched pairs vs. one of eight control pairs; P < 0.09). When treatments were reversed the following years (e.g., 1990 controls were exposed to enriched conditions in 1991), reproductive performance was not different between the groups (four of seven enriched pairs laid eggs vs. five of seven control pairs), although three pairs in the 1991 enriched group laid eggs which had not laid eggs before. These results are consistent with the idea that while enriched environments may enhance the probability of a first episode of egg laying in captivity, once pairs have laid eggs in captivity, little stimulation beyond that provided by nest box presentation is required to reinitiate egg laying. The environmental and social manipulations of the enriched conditions could be useful in increasing reproductive performance of captive Amazon parrots for the companion bird trade. © 1995 Wiley-Liss, Inc.     

Revisiting the influence of aggressive interactions on the survival of the first‐laid egg in crested penguins (genus Eudyptes)

Crested penguins Eudyptes spp. have evolved a unique form of breeding in which the first of two eggs laid is much smaller than the second and has a higher likelihood of being lost during egg laying and incubation. In this study, we quantified aggressive behaviour in nesting Snares penguins and undertook an egg survival analysis to examine which factors influence egg loss. During 120 h of observation of 50 nests, we recorded a total of 300 aggressive events in which females were repeatedly pecked, bitten and beaten. Aggressive events lasted from less than a minute to up to 55 min (mean 4.6 ± 7.4 min). Single males were the aggressor in 75% of aggressive events and in 50.7% of aggressive events the aggressor was identified as a neighbouring, breeding male. A greater percentage of the small first eggs (34%) were lost than the large second eggs (4%). We found that egg mortality was influenced by 1) whether the other egg within a nest had hatched, 2) who was present at the nest (father, mother or both) and 3) the average duration of aggressive events on the nest. When one egg within a nest had hatched, the other egg had a vastly increased mortality risk irrespective of aggression. However, long, aggressive events directed towards females after their partners had gone foraging, also increased the probability of egg loss. We suggest that the prolonged nest attendance by breeding males well beyond egg laying is in response to the high frequency of aggressive behaviour during this time. Our data show that A‐egg losses occur due to intraspecific aggression in this species. Further research is needed to clarify whether aggressive behaviour in breeding crested penguins is modulated by elevated testosterone levels in the males and whether any reproductive benefits accrue to the aggressors.     

The effects of heterospecifics and climatic conditions on incubation behavior within a mixed‐species colony

Parental incubation behavior largely influences nest survival, a critical demographic process in avian population dynamics, and behaviors vary across species with different life history breeding strategies. Although research has identified nest survival advantages of mixing colonies, behavioral mechanisms that might explain these effects is largely lacking. We examined parental incubation behavior using video‐monitoring techniques on Alcatraz Island, California, of black‐crowned night‐heron Nycticorax nycticorax (hereinafter, night‐heron) in a mixed‐species colony with California gulls Larus californicus and western gulls L. occidentalis. We first quantified general nesting behaviors (i.e. incubation constancy, and nest attendance), and a suite of specific nesting behaviors (i.e. inactivity, vigilance, preening, and nest maintenance) with respect to six different daily time periods. We employed linear mixed effects models to investigate environmental and temporal factors as sources of variation in incubation constancy and nest attendance using 211 nest days across three nesting seasons (2010–2012). We found incubation constancy (percent of time on the eggs) and nest attendance (percent of time at the nest) were lower for nests that were located < 3 m from one or more gull nest, which indirectly supports the predator protection hypothesis, whereby heterospecifics provide protection allowing more time for foraging and other self‐maintenance activities. To our knowledge, this is the first empirical evidence of the influence of one nesting species on the incubation behavior of another. We also identified distinct differences between incubation constancy and nest attentiveness, indicating that these biparental incubating species do not share similar energetic constraints as those that are observed for uniparental species. Additionally, we found that variation in incubation behavior was a function of temperature and precipitation, where the strength of these effects was dependent on the time of day. Overall, these findings strengthen our understanding of incubation behavior and nest ecology of a colonial‐nesting species.     

First nest descriptions,nesting biology and food habits for Bernier's Vanga,Oriolia bernieri,in Madagascar

Four nests of the rare and endemic Bernier's Vanga, Oriolia bernieri, were discovered; one in 1997, one in 1998, and two in 1999 on the Masoala Peninsula, northeastern Madagascar. At the 1998 nest, the female made 189 visits with 186 deliveries of nesting material during 34.6 h of observation. The female spent 9.2% (194.2 min) of the observation time building the nest while an immature male delivered nest material six times and spent 3.2 min at the nest placing the material. Nesting material included: 67.2% (125) decomposed root material, 24.7% (46) palm fibres, 6.5% (12) dry leaves, 1.1% (2) moss, and 0.5% (1) white plant dawn. In 41.0 h of observation during the incubation period the female incubated for 53% (21.7 h) of the time, the adult male for 32.3% (13.2 h), the immature male for 4.3% (1.8 h), and the nest was unattended for 10.4% (4.3 h). This breeding attempt foiled on day 13 of incubation when a Madagascar Harrier-Hawk, Polyboroides radiatus, ate the egg(s). At one of the 1999 nests, the incubation and nestling periods were 17 days each. Three young fledged during the middle of November. Of the 82 identified prey items recorded during the nestling period, 91% were invertebrates and 9% vertebrates. Spiders, crickets, cockroaches, and geckos represented the most numerous prey taken, totaling 77% of the identified prey.     

Incubation Feeding and Nest Attentiveness in a Socially Monogamous Songbird: Role of Feather Colouration,Territory Quality and Ambient Environment

Parental investment and environmental conditions determine reproductive success in wild‐ranging animals. Parental effort during incubation, and consequently factors driving it, has profound consequences for reproductive success in birds. The female nutrition hypothesis states that high male feeding enables the incubating female to spend more time on eggs, which can lead to higher hatching success. Moreover, both male and female parental investment during incubation might be signalled by plumage colouration. To test these hypotheses, we investigated relationships between male and female incubation behaviour and carotenoid and melanin‐based plumage colouration, territory quality and ambient temperature in the Great Tit Parus major. We also studied the effect of female incubation behaviour on hatching success. Intensity of male incubation feeding increased with lower temperatures and was higher in territories with more food supply, but only in poor years with low overall food supply. Female nest attentiveness increased with lower temperatures. Plumage colouration did not predict incubation behaviour of either parent. Thus, incubation behaviour of both parents was related mainly to environmental conditions. Moreover, there was no relationship between male incubation feeding, female nest attentiveness and hatching success. Consequently, our data were not consistent with the female nutrition hypothesis.     

Incubation feeding as a male tactic for early hatching

Male marsh tits, Parus palustris, regularly feed their mates from the beginning of nest building until hatching. Over three periods (the 15 days preceding egg formation, egg formation/laying and incubation) the number of food passes by the male to the female increased significantly. There was a significant negative relationship between the frequency with which the male fed the female in the nest during incubation and the length of the incubation period. Female blue tits, Parus caeruleus, experimentally supplied with food in the nestbox during incubation had a significantly shorter incubation period than control females. Clutches of experimentally fed females also tended to hatch more successfully. It is concluded that feeding of the female by the male is a nutritional contribution and that the shorter incubation period and increased hatching success enhance the fitness of both parents. However, the male should balance the benefits against the costs in time and energy and therefore not necessarily work at a maximal level. In accordance with this is the finding that the male's provisioning rate increased when ambient temperatures decreased. Adverse weather may jeopardize the whole or large proportions of the clutch, thereby significantly reducing the benefit from the current breeding attempt.     

Breeding behavior of a pair of free-living Andean Condors

ABSTRACT.   The breeding behavior of Andean Condors ( Vultur gryphus ) is known primarily from observations of captive pairs. This species is the only sexually dimorphic one in its family (Cathartidae), permitting comparison of the parental care provided by each sex. We examined the breeding behavior of a pair of condors over a period of 28 mo at a nest in Patagonia, Argentina. We first observed the pair near the nest site in January 2005. Courtship displays began in April and continued until October, when incubation started. The nestling hatched in early December 2005 and fledged in June 2006. The young condor first left the nest area 10 mo after hatching and was observed at the nest site for the last time 15 mo after hatching. Both adults incubated the egg and provisioned the nestling after hatching, and at least one adult was always present at the nest site for 2 mo post hatching. During the nesting period, the male visited the nest site more often, stayed for longer periods, interacted with the chick, and brought food more frequently than the female. Additional studies of the breeding biology of wild Andean Condors are needed to improve our understanding of their population ecology and demographics and to enhance conservation efforts.     

Experimental manipulation of female tail length did not cause differential allocation by males in the barn swallow

The evolution and maintenance of female ornamentation has attracted increasing attention, because the previous explanation, that is a non‐functional copy of functional male ornamentation, seems insufficient to explain female ornamentation. A post‐mating sexual selection, differential allocation, may be more common than pre‐mating sexual selection, but few studies have investigated differential allocation by males. Here, we studied differential allocation of incubation investment by male barn swallows Hirundo rustica, a model species for the study of sexual selection, because our previous correlative study demonstrated a positive relationship between female tail length and male incubation investment. We manipulated the length of the outermost tail feathers in females after clutch completion and examined whether males adjust incubation investment according to female ornamentation. Because extra‐pair paternity is virtually absent in the study population, we were able to study differential allocation based on the tradeoff between current and future reproductive investments, rather than the tradeoff between current paternal investment and additional mating effort. The experimental treatment had no significant effect on male nest attentiveness, whereas female tail length before manipulation predicted male nest attentiveness. The observed pattern is consistent with differential access; that is, well‐ornamented individuals have greater access to mates with high reproductive (parental) ability, rather than differential allocation during incubation. Alternatively, males can directly assess eggs in their nests, and thus, as seen in other species, males might adjust their incubation investment based on the egg characteristics of long‐tailed females.     

Latitudinal trends in within-year reoccupation of nest boxes and their implications

Multiple brooding can substantially increase the annual reproductive output of birds, and the propensity for multiple brooding can vary geographically. Thus, studies attempting to understand the evolution of geographic variation in nesting success need to account for variation in re‐nesting potential. However, direct assessment of rates of multiple brooding requires individually recognizable breeding adults, which are not generally available. We explore the possibility of comparing relative indices of multiple broodedness across a latitudinal gradient from studies of un‐banded birds locally restricted to nest boxes. We analyzed nest box reoccupation by a multiple‐brooding species, the eastern bluebird Sialia sialis, reported by volunteers in a citizen‐participation project (1998–2002) in which nest boxes were monitored throughout much of the breeding range of the bluebirds. We found nest boxes in the southern portion of the bluebird range (30° latitude) had, on average 17–33% higher likelihood of repeated egg‐laying, brooding, and successful fledging events than boxes in the north (48° latitude). Latitudinal variation in the reoccupation of nest boxes may indicate that either (1) the number of broods per female varies with latitude, (2) female breeding dispersal/site fidelity varies with latitude, (3) the density, distribution, and/or availability of suitable nest sites varies with latitude, or (4) observer bias varies with latitude. Various lines of evidence suggest that nest re‐occupancy is a useful index of latitudinal variation in re‐nesting. During the time‐frame of second attempts, first‐time box occupancy was as likely as second occupancy and approximately 45% more likely in the south than north, suggesting that, despite considerable breeding dispersal, observed trends in box reoccupation conservatively reflect latitudinal trends in the number of nest attempts/broods per female. Furthermore, despite a compressed nesting cycle in the north (shorter incubation and re‐nesting interval), the shorter duration of the breeding season in the north restricted the potential number of broods. Studies of banded birds are necessary to confirm the behavior underlying the latitudinal trends in box reoccupation.     

BREEDING BIOLOGY OF THE BEARDED VULTURE IN SOUTHERN AFRICA,PART I: THE PRELAYING AND INCUBATION PERIODS

Brown, C. J. 1990. Breeding biolo of the Bearded Vulture in southern Africa, Part I: The pre-laying and incubation periods. Ostrich 61: 24–32.

In southern Africa the Bearded Vulture Gpaetus barbatus lays its eggs in mid-winter. between the second half of May and the first week of July. Pairs became more active in their nesting areas about six weeks before laying and usually roosted there at night. Courtship flights were less frequent and demonstrative than in Eurasian birds and took place mainly in the late afternoons. During the pre-laying period most nest visits (77%) were to bring nesting material, 92% by the male. All nesting material was arranged by the female. Copulation was always preceded by allopreening, and occurred most frequently in the mornings. No copulation or courtship display took place after the first egg had been laid. Of 18 clutches, 16 (89%) contained two eggs and the remainder one egg. The laying interval was usually 3–5 days (range 2–9 days). Incubation started with the first egg and was evenly shared by both parents during the day, but only the female incubated at night, individual pairs maintained distinctive nest attendance and foraging period timetables, which allowed sufficient time for self-foraging by both parentes. No food was brought into the nest during the pre-laying and incubation periods, but in some pairs food was cached in nearby potholes in cliffs. The incubation period was 56–57 days.