Period Of Parental Care Research Articles

Juvenile Barn Swallows Hirundo rustica L. from late broods start autumn migration younger, fuel less effectively and show lower return rates than juveniles from early broods

Long‐distance migratory passerines may exhibit different post‐fledging rearing times between their early and late broods due to limited time and energy resources. This could affect the migratory fuelling behaviour, condition and fitness of juvenile birds. We analysed long‐term (13‐year) biometric data (body mass, fat score) on Barn Swallows ringed at the nest and later recaptured during their initial stages of autumn migration. The return rates of early‐ and late‐born juveniles after overwintering in Africa were further compared to estimate their fitness. We found that juveniles from late broods started migrating south on average 11 days younger compared with juveniles from early broods. Body masses of nestlings did not differ between early and late broods, but juveniles from late broods were in better condition after leaving the nest, possibly due to a longer period of parental care. Having started migration, juveniles from late broods were, however, less efficient in accumulating energy than juveniles from early broods. A younger departure age, together with less efficient fuelling of late brood juveniles, may partly explain the 39% lower return probability and hence lower fitness value of late‐brood juveniles. Our study is the first to show that juveniles from the early and late broods exhibit different fuelling behaviour and departure strategies (in terms of age and timing), which may be reflected in the fitness value of offspring.

Corticosterone Concentrations Reflect Parental Expenditure in Contrasting Mating Systems of Two Coucal Species

The period of parental care can be a demanding life-history stage because parents need to find sufficient resources to feed themselves and their offspring. Often, this is reflected by elevated baseline levels of glucocorticoids – hormones that regulate metabolism and energy allocation. During 10 breeding seasons, we studied plasma corticosterone (the major avian glucocorticoid) concentrations as a physiological correlate of parental expenditure in two closely related coucal species with fundamentally different mating systems: the sex-role reversed black coucal (Centropus grillii) with female competition and male-only care and the socially monogamous and biparental white-browed coucal (C. superciliosus). The two species live in the same habitat and share a similar breeding biology. However, female black coucals aggressively defend a territory and produce many eggs for their various male partners, and male black coucals feed their offspring much more frequently and rest less often than female and male white-browed coucals. These differences were reflected in baseline and stress-induced concentrations of corticosterone: male black coucals had higher baseline and stress-induced corticosterone concentrations when they were feeding young than outside a feeding context, and also the concentrations of female black coucals were higher during the main period of breeding when they defended territories and produced multiple clutches. In contrast, baseline and stress-induced concentrations of corticosterone in female and male white-browed coucals did not differ between periods when they were feeding young and periods without dependent offspring. Paradoxically, on an individual basis feeding effort was negatively related to baseline corticosterone in male black coucals and female white-browed coucals. In conclusion, corticosterone concentrations of coucals reflected differences in competition and parental roles and support the notion that a switch from biparental to uniparental care and an increase in mate competition may come at a physiological and energetic cost.

Do protected areas mitigate the effects of fisheries‐induced evolution on parental care behaviour of a teleost fish?

Abstract While the use of aquatic protected areas that exclude angling might be considered an evolutionarily enlightened management approach to dealing with fisheries‐induced evolution (FIE), there is little empirical data on the effectiveness of this approach at maintaining the diversity of phenotypic traits within protected areas. In species with paternal care, including largemouth bass (Micropterus salmoides), active nest‐guarding and aggression towards potential brood predators by males may render these individuals particularly vulnerable to capture by angling because of increased propensity to attack fishing lures/bait near their nests. Relative levels of aggression by these males during the parental care period correlates with their vulnerability to angling year round. Selective removal of more aggressive individuals by anglers should drive population‐average phenotypes towards lower levels of aggression. To assess the effectiveness of protected areas at mitigating FIE, the parental care behaviours of wild, free‐swimming male bass were compared during the early nesting period for bass within and outside protected areas in a lake in eastern Ontario. Nesting males within long‐standing aquatic protected areas closed to fishing for >70 years were more aggressive towards bluegill sunfish (Lepomis macrochirus), a potential nest predator, and patrolled larger areas around their nests compared with bass outside of sanctuaries. Males within protected areas were also more likely to strike at artificial fishing lures and were more prone to capture during angling events. Collectively, the findings suggest that the establishment of protected areas may promote phenotypic diversity such as more attentive and vigorous parental care, relative to areas open to angling. The extent to which this phenomenon occurs in other species and systems is likely to depend on the reproductive strategies of fish and their spatial ecology compared with protected area boundaries, and habitat quality within protected areas.

Prolonged Interspecific Care of Two Sibling Golden-winged Warblers (Vermivora chrysoptera) by a Black-and-white Warbler (Mniotilta varia)

ABSTRACT We observed a fledgling abandonment and adoption event that subsequently led to an extended period of interspecific parental care between a male Black-and-white Warbler (Mniotilta varia) and two radio-tagged fledgling Golden-winged Warbler (Vermivora chrysoptera) siblings. Both fledglings were initially accompanied by their maternal Golden-winged Warbler until 5 and 9 days after fledging. At this time, a male Black-and-white Warbler began feeding both fledglings, and maternal care ceased. In the 23 days we monitored the fledglings between onset of interspecific feeding and independence, the male Black-and-white Warbler was observed with at least one of the fledglings on 20 of those occasions. Furthermore, the Black-and-white Warbler was seen feeding at least one of the fledglings on 16 of those visits. We photographed several feeding events. The Black-and-white Warbler remained with the fledglings until they successfully reached independence 28 days post-fledging.

Breeding Biology of the Black-Faced Ibis (Theristicus melanopis) in Southern Chile

The breeding parameters of the Black-faced Ibis (Theristicus melanopis) in pastures of southern Chile between 5 July and 30 November 2014 were evaluated. Thirty active nests were monitored in an area of 31 km2, using a mirror mounted on a 13-m retractable aluminum pole. Each nest was visited once a week. The Black-faced Ibis presented an asynchronous posture period, with a maximum of three egg clutches. The first eggs were laid on 6 August 2014, and the mean incubation period was 28.66 (± 4.41) days. Mean clutch size during the first posture was 2.23 (± 0.73) with a range of one to three eggs per nest. None of the structural parameters of the nesting site evaluated were related to clutch size. The nests were oriented with a mean angle of 218° SW. Hatching of the chicks began on 25 September 2014, and the mean period of parental care lasted 36.67 (± 14.49) days. The apparent hatching success was 0.54, the fledging success was 0.40, and the total breeding cycle success was 0.23 independent young per nest. Predation explained the 56.7% nest loss. Chimango Caracara (Milvago chimango) was the main predator of eggs and chicks. The Mayfield estimator indicated a daily survival probability of 4.4% for the incubation cycle, 26.2% for the fledglings and 11.3% for the total breeding cycle.

Consequences of catch-and-release angling for black bream Spondyliosoma cantharus, during the parental care period: implications for management

Black sea bream Spondyliosoma cantharus is highly valued for its sporting and eating qualities. Due to its inshore spawning aggregations and male nest guarding behaviors, it is considered vulnerable to over-exploitation via recreational angling. Accordingly, greater uptake of the practice of catch-and-release (C&R) may provide some potential to limit the effects of angling on populations. Thus, the consequences of C&R for 40 S. cantharus (mean length 306 ± 10 mm) were assessed. Fish were sampled following their capture from charter boats by recreational anglers with varying levels of skill and experience. Of these fish, 17% were deeply hooked (e.g. in esophagus) and considered at high risk of post-release mortality (PRM). Blood lactate levels ranged between 0.40 and 2.60 mmol l − 1 (mean ± SE: 1.25 ± 0.09) and were significantly and positively correlated with fight time. Reflex impairments were observed in 32% of the catch, also suggesting an elevated probability of PRM. Hook damage was the only significant predictor of reflex impairment. The dominance of males (89%) across the catches highlighted the potential for additional indirect impacts of angling via the predation of eggs by conspecifics in the vacated nests of captured males. These results are discussed within the context of post-release performance of individual S. cantharus, the potential for C&R to limit impact at the population level and a need to consider future regulation of the fishery to ensure sustainability of stocks.

Patterns of hypothalamic GnIH change over the reproductive period in starlings and rats

Gonadotropin inhibitory hormone (GnIH) exerts powerful inhibitory effects on various levels of the vertebrate hypothalamic–pituitary–gonadal (reproductive) axis, yet little is known of how it might change naturally over the course of reproduction. We characterized patterns of hypothalamic GnIH cell abundance over the reproductive period in two popular models used for the study of reproductive endocrinology: European starlings (Sturnus vulgaris) and Sprague-Dawley rats (Rattus norvegicus). We also examined the effects on an unpredictable change in the environment on GnIH cell abundance during the reproductive period, specifically during the period of parental care, by simulating a nest predation event and removing eggs/pups. In both species, we report changes in GnIH cell abundance are occurring at similar reproductive time points but are not always directionally parallel; this may be due to a difference in life histories and physiology mediating parental care. We discovered that cells immunoreactive for the GnIH peptide in male and female starlings are most highly abundant on the first day of incubation and the first day after the first chick hatches. Conversely in rats, GnIH cell abundance decreases in dams on the first day after pups are born. In both male and female starlings and female rats, GnIH cell abundance increases in response to egg/pup loss, indicating that GnIH responds to an unpredictable change in the environment in a potentially conserved fashion. These changes in GnIH cell abundance during the reproductive period inspire further investigation of its adaptive role in reproductive physiological events and behaviors, especially parental care.

Non-adaptive territory selection by a bird with exceptionally long parental care.

High-quality territories are expected to provide greater fitness return for breeding individuals and, thus, are likely to have higher long-term occupation rate in comparison to low-quality territories. However, if environmental and ecological cues used for territory selection cannot reliably predict true territory quality, a mismatch between preferences and fitness may occur. We suggest that this kind of non-adaptive territory selection is more likely in species with long reproductive cycles, as a long time interval between territory establishment and young fledgling should reduce predictability of conditions during the critical stages of brood care. In this study, we investigated adaptiveness of territory selection in a migratory bird with exceptionally long parental care, the mute swan Cygnus olor, which requires over four months to complete the entire reproductive cycle from egg laying to young fledging. For this purpose, we collected information on the long-term (10–19 years) occupancy of 222 swan breeding territories and correlated it with reproductive performance (n = 1,345 breeding attempts) and body condition of breeding adults. We found that long-term occupancy positively correlated with the timing of breeding, suggesting that individuals settled earlier in the attractive, frequently occupied territories. By contrast, we found no relationship between territory occupancy and reproductive output (hatching and fledging success) or adult body condition. The results indicate that at the time of territory selection swans might not be able to reliably assess territory quality, likely due to: (1) exceptionally long period of parental care, which reduces temporal correlation between the conditions at the time of territory selection and conditions during chick rearing; and (2) unpredictability of human-related activities that had a major impact on reproductive output of swan pairs in our population.

When ambient noise impairs parent-offspring communication

Ambient noise has increased in extent, duration and intensity with significant implications for species’ lives. Birds especially, because they heavily rely on vocal communication, are highly sensitive towards noise pollution. Noise can impair the quality of a territory or hamper the transmission of vocal signals such as song. The latter has significant fitness consequences as it may erode partner preferences in the context of mate choice. Additional fitness costs may arise if noise masks communication between soliciting offspring and providing parents during the period of parental care. Here, we experimentally manipulated the acoustic environment of blue tit (Cyanistes caeruleus) families within their nest boxes with playbacks of previously recorded highway noise and investigated the consequences on parent-offspring communication. We hypothesized that noise interferes with the acoustic cues of parental arrival and vocal components of offspring begging. As such we expected an increase in the frequency of missed detections, when nestlings fail to respond to the returning parent, and a decrease in parental provisioning rates. Parents significantly reduced their rate of provisioning in noisy conditions compared to a control treatment. This reduction is likely to be the consequence of a parental misinterpretation of the offspring hunger level, as we found that nestlings fail to respond to the returning parent more frequently in the presence of noise. Noise also potentially masks vocal begging components, again contributing to parental underestimation of offspring requirements. Either way, it appears that noise impaired parent-offspring communication is likely to reduce reproductive success.

Demography of a ground nesting bird in an urban system: are populations self-sustaining?

Urbanization poses threats to earth’s biota, and retention of remnant native habitat in protected areas within expanding urban boundaries may help alleviate threats to wildlife. However, it is unclear for nearly all nonsynanthropic (i.e., not benefiting from an association with humans) species whether vital rates in urban habitats can sustain populations or if populations persist only through immigration from outside the urban boundary. We conducted a three-year study of spotted towhees (Aves: Pipilo maculatus) breeding in four undeveloped parks in Portland, OR, USA, to measure park-specific seasonal reproductive output (F) and annual adult survival (SA). We developed a stochastic model that combined F and SA with an estimate of first-year survival to measure population growth rate (λ) in all parks assumed to be closed to immigration. F differed among parks but SA did not. Relatively high F was possible because many pairs raised >1 brood/season. When combined with empirical estimates of survival through the 30-day period of post-fledging parental care (SD = 0.645), only 2 of 4 parks were self-sustaining (i.e., λ > 1.0). However, SD reflected substantial loss of fledglings to domestic cats (Felis catus). Assuming no loss to cats and either partial compensatory or additive mortality of fledglings substantially improved prospects of population persistence for declining (sink) populations. Moreover, allowing low levels of immigration to sinks reversed population declines in most parks even when vital rates were insufficient to maintain populations. Our results suggest that nonsynanthropic bird species can persist in urban landscapes, but also that offspring mortality in the post-fledging period may be a critical determinant of population viability.

Are prenatal maternal resources more important in competitive than in benign postnatal environments?

ABSTRACT According to theoretical models, the optimal solution of the life-history trade-off between the number and size of offspring depends on the quality of the environment. Offspring size should be more important for their fitness in more competitive environments. This idea was rarely experimentally tested in taxa with prolonged periods of parental postnatal care, such as in birds. Here we manipulated the offspring rearing environment by enlarging or reducing brood size. Enlarged broods suffered greater mortality rates and raised smaller fledglings. Egg size had a significant positive effect on fledging mass and length of tarsus and a nonsignificant effect on wing length. These effects were similar in enlarged-sized as well as reduced-sized broods. We only found a tendency for the predicted interaction between treatment and egg size in the case of nestling mass where egg size had a positive effect in enlarged broods but none in reduced broods. In contrast, in one year we found an opposite interaction ...

Reproductive and parental care physiology of Cichlasoma dimerus males

The South American cichlid fish Cichlasoma dimerus presents a high breeding frequency and biparental care of the eggs and larvae. The male parental care period was divided in four different phases according to the developmental degree of the offspring: pre-spawning activity (MP, day 0), guarding eggs (ME, one day after fertilization (1 DAF)), guarding hatched larvae (MHL, 3 DAF), and guarding swimming larvae (MSL, 8 DAF). The aim of this study was to characterize male reproductive physiology by measuring steroid hormone plasma levels and analyzing testes cellular composition. Males exhibiting pre-spawning activity showed 8.4 times higher 11-ketotestosterone and 5.63 times higher testosterone levels than MHL. No differences were observed in estradiol and cortisol levels among the different phases. The cellular composition of the testes varied during the reproductive and parental care periods. Testes of MP were composed of 50% of spermatozoa, whereas spermatogonia type B and spermatocytes were predominant in the subsequent parental phases. A morphometric analysis of Leydig cells nuclear area revealed that MP and ME’s Leydig cells averaged 1.27 times larger than that those of MHL and MSL and was positively correlated with circulating 11-KT and T levels. Hence, C. dimerus males showed important changes in its hormonal profiles and testicular cellular composition throughout the reproductive and parental care period.

Dominance network structure across reproductive contexts in the cooperatively breeding cichlid fish Neolamprologus pulcher

Abstract While a large number of studies have described animal social networks, we have a poor understanding of how these networks vary with ecological and social conditions. For example, reproductive periods are an important life-history stage that may involve changes in dominance relationships among individuals, yet no study to date has compared social networks of dominance interactions (i.e. dominance networks) across reproductive contexts. We first analyzed a long-term dataset on captive social groups of the cooperatively breeding cichlid Neolamprologus pulcher, and found that eviction events were significantly more common around reproduction than expected by chance. Next, we compared the structure of dominance networks during early parental care and non-reproductive periods, using one of the first applications of exponential random graph models in behavioral biology. Contrary to our predictions, we found that dominance networks showed few changes between early parental care and non-reproductive periods. We found no evidence that dominance interactions became more skewed towards larger individuals, became more frequent between similar-sized individuals, or became more biased towards a particular sex during parental care. However, we did find that there were relatively more dominance interactions between opposite-sex dyads in the early parental care period, which may be a by-product of increased sexual interactions during this time. This is the first study in behavioral ecology to compare social networks using exponential random graph modeling, and demonstrates a powerful analytical framework for future studies in the field.

Sex allocation, juvenile mortality and the costs imposed by offspring on parents and siblings.

Generally, sex-specific mortality is not expected to affect optimal patterns of sex allocation. Several authors have, however, made verbal arguments that this is not true if juvenile mortality is sex specific during the period of parental care. Here, we provide formal mathematical models exploring the effect of such mortality on optimal sex allocation. We confirm the prediction that biased production of the sex with higher mortality during care is favoured. Crucially, however, this is only true when juvenile mortality in the period of parental care frees up resources for their current/future siblings (i.e. the saved investment is transferable). Furthermore, we show that although optimal sex allocation is consistent with the theory of equal investment (as asserted by previous authors), thinking in terms of equal investment is not readily feasible in some scenarios. We also show that differences in early mortality overcome biased sex allocation such that the sex ratio at independence is generally, but not always, biased in the opposite direction from that at birth. Our models should prove useful to empiricists investigating the effect of sex-specific juvenile mortality and antagonistic sibling interactions on sex allocation.

Factors influencing cannibalism in the plainfin midshipman fish

Cannibalism of young is a common yet seemingly paradoxical phenomenon observed across a wide variety of taxa. Understanding this behaviour in the context of parental care remains a challenge for evolutionary biologists. A common adaptive explanation for the consumption of offspring is that it serves to increase the current or future reproductive success or survival of the cannibalistic parent by replenishing energy stores and facilitating continued care for any remaining young. Another explanation is that cannibalism may be a competitive response to cuckoldry or lowered certainty of parentage. We tested these ideas using the plainfin midshipman fish, Porichthys notatus, a species with an extended period of male-only parental care and documented offspring cannibalism. We found that the occurrence of cannibalism was not linked to the deterioration of body condition, but instead was most frequent during periods of high intrasexual competition and nest take-overs. Our results suggest that cannibalism is not driven by the energetic demands of parental care, but instead by competition among males for nests and females, and the resulting low paternity stemming from both nest take-overs and cuckoldry.

Deep-Sea Octopus (Graneledone boreopacifica) Conducts the Longest-Known Egg-Brooding Period of Any Animal

Octopuses typically have a single reproductive period and then they die (semelparity). Once a clutch of fertilized eggs has been produced, the female protects and tends them until they hatch. In most shallow-water species this period of parental care can last from 1 to 3 months, but very little is known about the brooding of deep-living species. In the cold, dark waters of the deep ocean, metabolic processes are often slower than their counterparts at shallower depths. Extrapolations from data on shallow-water octopus species suggest that lower temperatures would prolong embryonic development periods. Likewise, laboratory studies have linked lower temperatures to longer brooding periods in cephalopods, but direct evidence has not been available. We found an opportunity to directly measure the brooding period of the deep-sea octopus Graneledone boreopacifica, in its natural habitat. At 53 months, it is by far the longest egg-brooding period ever reported for any animal species. These surprising results emphasize the selective value of prolonged embryonic development in order to produce competitive hatchlings. They also extend the known boundaries of physiological adaptations for life in the deep sea.

Regulation of hypothalamic–pituitary–interrenal axis function in male smallmouth bass (Micropterus dolomieu) during parental care

Male smallmouth bass (Micropterus dolomieu) provide sole parental care until offspring reach independence, a period of several weeks. During the early parental care period when males are guarding fresh eggs (MG-FE), cortisol responsiveness is attenuated; the response is re-established when males reach the end of the parental care period and are guarding free-swimming fry (MG-FSF). It was hypothesized that attenuation of the cortisol response in male smallmouth bass during early parental care reflected modulation of hypothalamic–pituitary–interrenal (HPI) axis function. Male smallmouth bass were sampled at the beginning (MG-FE) and end of the parental care period (MG-FSF), before and/or 25min after exposure to a standardized stressor consisting of 3min of air exposure. Repeated sampling of stressed fish for analysis of plasma cortisol and adrenocorticotropic hormone (ACTH) levels was carried out. Males significantly elevated both plasma cortisol and ACTH levels when guarding free-swimming fry but not during early parental care. Control and stressed fish were terminally sampled for tissue mRNA abundance of preoptic area (POA) and hypothalamic corticotropin-releasing factor (CRF) as well as head kidney melanocortin 2 receptor (MC2R), steroidogenic acute regulatory protein (StAR) and cytochrome P450 side chain cleavage enzyme (P450scc). No significant differences in either hypothalamus CRF or head kidney P450scc mRNA abundance were found across parental care stages or in response to stress. However, POA CRF mRNA abundance and interrenal cell MC2R and StAR mRNA abundances failed to increase in response to stress in MG-FE. Thus, the attenuated cortisol response in males guarding fresh eggs may be explained by hypoactive HPI axis function in response to stress. The present is one of few studies, and the first teleost study, to address the mechanisms underlying resistance to stress during the reproductive/parental care period.

When males stop having sex: adaptive insect mating tactics during parental care

The theory of prudent sperm allocation predicts that males should reduce their investment in sperm transfer when their mate's propensity to produce offspring is low. Furthermore, if mating is costly for females, they would benefit from signalling this propensity to males to keep them from attempting to mate. Here we document a remarkable flexibility in insect mating tactic during the period of parental care. Extensive video observations in the biparental burying beetle Nicrophorus vespilloides revealed that pairs mate frequently before and during oviposition, temporarily discontinue their sexual activity while young larvae are present, and resume mating when males are close to leaving the brood. An experiment, in which we switched males at different time intervals and determined their P2 value (i.e. the proportion of progeny sired by the second male), confirmed the lack of mating activity during the first few days of larval care and its resumption later in parental care. Females cease laying eggs when caring for larvae, but females will resume egg laying if none of the larvae from their first clutch reach the carcass. We manipulated females into producing such replacement clutches by withholding their larvae, and we found that in this situation males did not cease to mate, but continued to engage in frequent copulations. Hence, males have the ability to assess a female's propensity for oviposition during the period of parental care. Further experiments demonstrated that males do not use the presence or absence of larvae as a cue to adjust copulation rate, but instead use female-produced cues of reproductive state. Therefore, our study reveals that female beetles express cues that display their reproductive condition and males have evolved the ability to detect these cues and respond with prudent sperm allocation. Our findings further contribute to the developing picture of the sophisticated mating tactics that insects employ.

Trade-offs between personal immunity and reproduction in the burying beetle, Nicrophorus vespilloides

We know that parental investment and immune investment are costly processes, but it is unclear which trait will be prioritised when both may be required. Here we address this question using the burying beetle Nicrophorus vespilloides, carrion breeders that exhibit biparental care of young. Our results show that immunosuppression occurs during provision of parental care. We measured Phenoloxidase (PO) on Day 1-8 of the breeding bout and results show a clear decrease in PO immediately from presentation of the breeding resource onwards. Having established baseline immune investment during breeding we then manipulated immune investment at different times by applying a wounding challenge. Beetles were wounded prior to and during the parental care period and reproductive investment quantified. Different effects on reproductive output occur depending on the timing of wounding. Challenging the immune system with wounding prior to breeding does not affect reproductive output and subsequent Lifetime Reproductive Success (LRS). LRS is also unaffected by applying an immune elicitor prior to breeding, though different arms of the immune system are up/downregulated, perhaps indicating a trade-off between cellular and humoral immunity. In contrast, wounding during breeding reduces reproductive output and to the greatest extent if the challenge is applied early in the breeding bout. Despite being immunosuppressed, breeding beetles can still respond to wounding by increasing PO, albeit not to pre-breeding levels. This upregulation of PO during breeding may affect parental investment, resulting in a reduction in reproductive output. The potential role of juvenile hormone in controlling this trade-off is discussed.

Observations on breeding behavior of the White-eared Night Heron (Gorsachius magnificus) in northern Guangdong, China

The White-eared Night Heron (<i>Gorsachius magnificus</i>) is a Class II protected species in China. It is difficult to observe in the field and its population is small. The present study reports a new distribution site in Nanxiong County, in northern Guangdong Province, where observations of an active nest were made from 4 May to 14 July 2012, the first time consecutive observations have been made for a period of more than two months. The adults flew away from the nest at night, with a peak at 19:00-20:00 and returned in the mornings with a peak at 04:30-05:30. The peak time for feeding young was at 05:00-05:30, accounting for 26.5% of total feeding activities. No feeding occurred from 10:00 to 16:00. The results of our study of its behavior explain why the White-eared Night Heron is usually observed in the evening just before dark, or in the morning before sunrise, at least during the breeding season. There were about 67 days from hatching to fledging, longer than the fledging time of most heron species. This study is the first to cover the entire period of parental care and fills a gap in previous knowledge.