Brood Age Research Articles

Lazy males and hardworking females? Sexual conflict over parental care in a brood parasite host and its consequences for chick growth

Due to the costs of parental care, a conflict of interests often arises between mates wherein each prefers the other to invest more. As with parents raising their own offspring, hosts of brood parasites also exhibit negotiations over investment, becoming particularly intensive when parasite demands are high. Lack of cooperation between the partners may eventually affect the condition and fledging success of the young. Here, we investigate the magnitude of sexual conflict over food provisioning in socially polygynous great reed warblers (Acrocephalus arundinaceus) rearing either a parasitic common cuckoo (Cuculus canorus) or their own nestlings and its consequences for chick growth. We found that, overall, males provided less food than females, and that polygynous males provided less food per nest than monogamous males. Moreover, polygynous males provisioning two simultaneous broods supplied their own offspring in relation to age and type (cuckoo/host) of the other brood. Females, unlike males, delivered food amount almost irrespective of social status. The difference in contribution between polygynous males and their mates was most pronounced in nests with a cuckoo. In any case, reduced paternal assistance had no significant effect on growth performance of nestlings. In cuckoos, however, this result may be biased as we could not consider a relatively high proportion of secondary cuckoos that died before their growth parameters could be ascertained. Although not detected in chick growth, host sexual conflict over food provisioning may impose a cost on cuckoos in terms of increased mortality in secondary nests.

Mid‐contract management of Conservation Reserve Program grasslands provides benefits for ring‐necked pheasant nest and brood survival

AbstractConservation Reserve Program (CRP) fields may provide good habitat for nesting and brood‐rearing ring‐necked pheasants (Phasianus colchicus) during early stages of succession. But, the success of hens in early successional CRP, relative to late successional CRP and other grassland habitats, has yet to be evaluated. The reproductive period is especially critical for populations of pheasants, and CRP's benefits to hens and chicks may decrease as fields age because of loss of vegetative diversity, decrease in vegetation density, and accumulation of residual litter. During 2005–2006, we evaluated spatial and temporal variation in nest and brood survival for radio‐marked hen pheasants in areas of northeastern Nebraska where portions of CRP fields had been recently disced and interseeded (DICRP) with legumes. Nests in DICRP tended to have a higher daily survival rate (0.984; 95% CI: 0.957–0.994) than nests in grasslands (including CRP) that were unmanaged (0.951; 95% CI: 0.941–0.972). The probability of 23‐day nest success was 0.696 (95% CI: 0.631–0.762) for DICRP and 0.314 (95% CI: 0.240–0.389) for unmanaged grasslands. Daily brood survival rates varied by habitat type, brood age, and date of hatch. The probability of a brood surviving to day 21 was 0.710 (95% CI: 0.610–0.856). Brood survival rates increased with time spent in DICRP and as the brood aged. Survival decreased as broods spent more time in cropland and peaked seasonally with broods that hatched on 15 June. Brood survival probability, to 21 days, would be reduced to 0.36 (95% CI: 0.100–0.701) if broods in our sample had not used DICRP. We combined nest and brood survival in a productivity model that suggested 2,000 hens, in a landscape with no DICRP, would produce 1,826 chicks, whereas the same hens in a landscape of 100% DICRP would produce 5,398 chicks. Production of first‐year roosters more than doubled when hens nested in DICRP. Without DICRP, population growth rates of pheasant populations usually declined; with DICRP, populations stabilized with at annual survival rates of 0.3 or greater. The positive response of nest and brood survival to discing and interseeding CRP provides further evidence that CRP fields must be managed to optimize wildlife benefits. © 2012 The Wildlife Society.

Do brood sex ratio, nestling development and sex affect fledging timing and order? An experimental study on great tits

The process of nest leaving (fledging) in hole-breeding passerines is largely unexplored, although it is potentially an important facet of reproduction. We used the great tit, Parus major, to investigate whether fledging timing and order were affected by nestling development and sex, as well as the sex ratio in the brood the nestlings were raised in. Because of the difference in size and competitiveness between male and female nestlings, we expected to find an effect of sex and brood sex ratio (BSR) on the process of fledging. To explore its effect on fledging experimentally, we manipulated BSR by swapping 6-day-old nestlings of both sexes. We implanted transponders in all 14-day-old nestlings to determine timing and order of fledging. The brood age at fledging was best explained by average wing length of the brood (negative), average body mass of the brood (positive) and hatching date (negative). In contrast to our hypothesis, BSR did not affect fledging time. Also, the asynchrony of fledging within broods did not depend on BSR. Within broods, fledging order was not affected by sex or by the interaction between sex and BSR. Nestlings with long wings on day 14 fledged earlier than nestmates with shorter wings. Although females were lighter at day 14, they had similar length wings as their male nestmates. Nestlings should keep up with their nestmates during development, because developmental status relative to nestmates, rather than sex-specific competition, influenced the process of fledging.

When and why do smallmouth bass abandon their broods? The effects of brood and parental characteristics

Abstract Variation in brood abandonment was explored by conducting partial brood removals from smallmouth bass, Micropterus dolomieu Lacepède, nests in two north temperate lakes. In both lakes, percent of the brood removed had no effect on nest failure rates. Nest failure prior to offspring swim‐up was more common, but unrelated to brood size after removal, in the lake with higher post‐spawning mortality and lower growth and fecundity. Brood size after removal was negatively related to nest failure in the lake with high survival, growth and fecundity. Nests guarded by young males failed more frequently than those of old males, and young broods failed more frequently than old broods. Dynamic programming and logistic regression models developed to predict nest fate worked better for the lake with selective pressures that theoretically favoured abandonment (e.g. high post‐spawning mortality). Both models identified male age and brood age as important factors in predicting nest fates. Because nest success is related to the age of the parent, this could have consequences for overall nest success for populations with different demographics.

Parental investment in relation to offspring quality in the biparental cichlid fish Pelvicachromis taeniatus

Theory predicts that parents should adjust their parental investment to the reproductive value of the brood. Previous studies have mainly investigated the relationship between brood size, brood age and the intensity of care. However, the impact of brood quality traits such as the offspring’s average body size on parental investment has received relatively little attention. We examined the parental response to brood quality in the biparentally brood-caring cichlid fish Pelvicachromis taeniatus. We manipulated offspring quality by manipulating the food availability for the free-swimming fry and measured the parental response over 4 weeks. Generally, care decreased over the 4 weeks suggesting that parents adjust care to decreasing offspring vulnerability. However, parents of relatively low-quality broods, that is, of broods with relatively small average individual body size, showed a greater reduction in care than parents of high-quality broods resulting in a significant difference in care provided in the fourth week. The result suggests that parents adjust their care to brood quality and supports the predictions of the parental investment theory. Furthermore, mothers of high-quality fry were significantly more aggressive towards their partner than mothers of low-quality fry. This result is discussed in the context of parental response to brood value. Generally, females invested more in brood care than males.

Enemy Recognition of Reed Warblers (Acrocephalus scirpaceus): Threats and Reproductive Value Act Independently in Nest Defence Modulation

AbstractOrganisms should respond more aggressively towards species perceived as a danger to their offspring, but intensity of defence may be gauged by the value of current offspring weighed against the value of future reproductive opportunities. We tested whether defensive responses of nesting reed warblers (Acrocephalus scirpaceus) are the result of an interaction effect between the type of stimulus confronted and the value of the warbler’s nesting attempt. We quantified the ability of reed warblers to discriminate among brood parasites, nestling predators and non‐threatening species at different stages of the breeding cycle. We also determined whether variables that influence the value of offspring, such as time of season, size and age of clutch or brood, and time of day and number of visits to the nest, explain variation in the intensity of defence recorded during the egg and nestling stages. Responses to the three stimuli differed significantly, as reed warblers consistently directed their mobbing calls and attacks towards parasites, whereas they were less conspicuous when confronted with models of predators. Reed warblers modulated their responses towards each stimulus in accordance with the threat each posed at a specific nesting stage, whereas they were not affected by other variables relative to their reproductive potential. The churr call, however, was uttered independently of the stimulus, as it was triggered by the mere presence of nestlings in the nest.

Effect of Brood Reduction on Nest Abandonment of Smallmouth Bass

AbstractSmallmouth bass Micropterus dolomieu are well known for vigilantly guarding their nests, which is done solely by the males. Because parental care is costly, smallmouth bass are faced with a trade‐off between current and future reproduction. If the male foregoes current reproductive efforts and abandons his nest, he may be better able to prepare for future efforts. In this article, we present field data on the effect of brood reduction on nest abandonment and explore the role of male age, brood size, and brood age on nest abandonment. We removed 0, 25, 50, or 75% of the brood from males' nests in Lake Opeongo, Ontario, during the summers of 2007 and 2008 and observed the response (nest success or failure). Across all treatments, 22 of 105 nests (21%) failed and were abandoned, but there was no significant difference among treatments. However, fish that abandoned their nests were significantly younger and had fewer offspring at the time of abandonment than did those that did not. In addition, younger nests were more likely to be abandoned than older nests. Our results differ from those of previous brood reduction experiments, although they match parental care theory overall.

Parental differences in brood provisioning by Hen Harriers Circus cyaneus

Capsule Females varied their provisioning patterns according to brood age and brood size, whereas males did not. Aims To quantify how parents balance the needs of their offspring for food and protection. Methods We studied 13 nests from hides and spent on average 101 hours per nest monitoring prey types, provisioning rate and the time spent at the nest by both sexes in relation to brood size and brood age. Results Males always provided more food than females. Males brought similar amounts of prey items irrespective of brood size and nestling age, whereas females brought more prey and bigger items to larger and older broods. Females spent less time brooding larger broods, particularly early on. Conclusions Hen Harrier parents share the provisioning burden, with each parent delivering prey as a function of brood care requirements, hunting capability and the behaviour of the other parent.

Predation risk of whole-clutch filial cannibalism in a tropical skink with maternal care

Filial cannibalism, the process of eating one’s own offspring, is relatively common in some animal species and has been particularly well studied in fishes. However, whole-clutch filial cannibalism committed by terrestrial vertebrate parents has rarely been reported. In this study, I describe the existence of whole-clutch filial cannibalism in the long-tailed skink, Mabuya longicaudata, on Orchid Island, Taiwan. When skinks encountered intruders against which they could defend themselves, such as the egg-eating snake, Oligodon formosanus, and the agamid, Japalura swinhonis, most M. longicaudata females would either attack (O. formosanus) or ignore (J. swinhonis) the predator, but when the frequency of intrusions by the intruder, O. formosanus, increased, whole-clutch filial cannibalism occurred. When females feel threatened by O. formosanus, the best choice (especially for gravid females) may be to eat their entire clutch of eggs. This behavior has evolved in this skink, thus providing a rare case of whole-clutch cannibalism by a mother reptile. Two existing hypotheses (decreasing brood size and brood age) to explain wholeclutch filial cannibalism suggest that cannibalistic parents may eat the entire clutch when the costs of caring outweigh the expected benefits. In the current study, my results suggest that whole-clutch filial cannibalism is primarily induced by the presence of predators. Thus, I suggest a hypothesis of predation risk of whole-clutch filial cannibalism, in which filial cannibalism by M. longicaudata increases as the predation risk to its offspring increases. Key words: eggs cannibalized by a skink, Mabuya longicaudata, pregnancy, snake-induced behavior. [Behav Ecol]

Post-hatching parental care behaviour and hormonal status in a precocial bird

In birds, the link between parental care behaviour and prolactin release during incubation persists after hatching in altricial birds, but has never been precisely studied during the whole rearing period in precocial species, such as ducks. The present study aims to understand how changes in parental care after hatching are related to circulating prolactin levels in mallard hens rearing ducklings. Blood was sampled in hens over at least 13 post-hatching weeks and the behaviour of the hens and the ducklings was recorded daily until fledging. Contacts between hens and the ducklings, leadership of the ducklings and gathering of them steadily decreased over post-hatching time. Conversely, resting, preening and agonistic behaviour of hens towards ducklings increased. Plasma prolactin concentrations remained at high levels after hatching and then fell after week 6 when body mass and structural size of the young were close to those of the hen. Parental care behaviour declined linearly with brood age, showed a disruption of the hen-brood bond at week 6 post-hatching and was related to prolactin concentration according to a sigmoid function. Our results suggest that a definite threshold in circulating prolactin is necessary to promote and/or to maintain post-hatching parental care in ducks.

PARENTAL INVESTMENT IN SWAN GEESE IN AN URBAN ENVIRONMENT

I studied brood-rearing behavior of introduced Swan Geese (Anser cygnoides) in Heidelberg, Germany during 2002 and 2003. Two hypotheses were tested: (1) division of labor between males and females is similar to that of wild Anser species, and (2) parental investment (vigilance behavior) is adjusted for brood size. I used 10-min sessions of focal animal sampling during which I simultaneously recorded the behavior of the male, the female, and a majority of the juveniles every 15 sec. Division of labor was similar to that observed in wild Anser populations: males were more vigilant whereas females spent more time feeding during the first 4 weeks of brood-rearing. As brood-rearing progressed, vigilance and agonistic behavior by both males and females decreased, whereas juveniles decreased feeding and increased vigilance. Adults (males and females combined) adjusted vigilance for brood size. A general linear model showed a significant influence of both brood size and brood age on parental vigilance.

Nest and Brood Survival of Lesser Prairie-Chickens in West Central Kansas

We evaluated the effect of habitat use and other sources of variation on survival of lesser prairie-chicken (Tympanuchus pallidicinctus) and greater prairie-chicken (Tympanuchus cupido) nests and broods. Daily nest and brood-survival probabilities were a function of a quadratic time trend, and both declined as the season progressed. Daily nest survival was negatively associated with nest age, and daily brood survival was positively associated with brood age. Lastly, broods tended by adult females had higher daily survival rates than broods reared by subadult females. The probability of a nest surviving from 10 May to 1 June was 0.72 (SE = 0.06). The probability of a brood surviving from 1 June to 30 July (hatch to 60 days posthatch) was 0.49 (SE = 0.19) and 0.05 (SE = 0.03) for broods reared by adults and subadults, respectively. Although nesting females and females with broods were using Conservation Reserve Program grasslands, there appeared to be no benefit to nest and brood survival during our study. Instead, age of the nest and brood, timing during the season, age of the brooding female, and precipitation during brooding were more important predictors of survival. Further experimentation is needed to determine the mechanisms responsible for decreased nest and brood survival throughout the season. Results from such research could be used to formulate management strategies to improve nest and brood survival.

Paternity and paternal effort in the pumpkinseed sunfish

Theoretical models suggest that males should adjust their parental effort according to paternity when parental effort is costly, paternity varies amongclutches, and males have a cue to assess paternity. To date,nearly all tests of this theory havebeen conducted using birds as model organisms. In this study we examined these three factors and the relationship between paternity and male parental care in a fish system. In the pumpkinseed sunfish (Lepomis gibbosus), parental care is provided exclusively by males (parentals), but some males (sneakers) parasitize others by sneaking fertilizations. Parental males significantly lost weight during the parental care period. Clutch size and amount of parental effort did not affect a male’s probability of obtaining more eggs. Paternitywasvariableamongbroods.Theproportionofyoungsiredbyaparentalmalewasnotassociatedwithfrequencyoffanning eggs or defense of hatched young, but was positively correlated with levels of nest defense during the egg stage. Egg survivorship might restrict an adjustment of fanning behavior, and a general decline in parental behavior (with brood age) might explain the lack of adjustment once the eggs hatch. Parental males did not adjust their care when we experimentally manipulated one possible cue of paternity. Together, these results indicate that male pumpkinseeds do adjust their care in relation to paternity, but the cues used to assess paternity are not clear. Key words: alternative strategies, parental care, paternity, pumpkinseed sunfish. [Behav Ecol]

Food Provisioning in Red-Necked Grebes (Podiceps Grisegena) at Common Carp (Cyprinus Carpio) Ponds

Parental feeding patterns were studied in red-necked grebe (Podiceps grisegena) broods throughout the entire period of parental care in a common carp (Cyprinus carpio) fish-pond area in SE Poland in 1993–2002. Fish formed a substantial part of prey provided to the flightless young from their second week of life. Although the numbers of large invertebrates and tadpoles, the alternative prey to fish, did not decrease during the chick rearing period, grebe parents gradually shifted from delivering predominately invertebrates to delivering fish, and the average size of fish fed to chicks increased with brood age. Broods with relatively high fledging success (at least two chicks fledged) had a larger proportion of fish in their diet than broods seriously reduced because of undernourishment. The dive duration of foraging grebe parents did not differ between carp, wild fish and non-fish prey, but carp prey required significantly more time for handling. The percentage of prey rejected by chicks increased over the prefledging period from 2 to 24%. Of the prey rejected, 82% were fish apparently too large for the young to swallow. Fish prevalence in the diet of red-necked grebe chicks at carp ponds contradicts the results of other studies on the feeding habits of the nominative subspecies during breeding season. However, the red-necked grebe is a gape-limited predator and the piscivory of the chicks is limited to small-bodied fish.

Emergency queen rearing in honeybee colonies with brood of known age

In four honeybee colonies, queens were isolated on empty combs for 8 consecutive days, so that in every colony there were 8 combs containing brood of known age. Afterwards, the colonies were dequeened and the process of emergency queen rearing was observed. The average interval from egg laying to queen cell capping was 8.8 days and ranged from 7 to 12 days. The average interval from queen cell capping to queen emergence was 7.2 days and ranged from 5 to 8 days. The whole development time from egg laying to queen emergence was 15.7 days, ranging from 14 to 18 days. The age of brood at the moment of dequeening positively correlated with both the time of capping and the total queen development time. The average age of brood (at time of dequeening) around which queen cells were built was 3.0 days. However, higher proportions of queen cells with younger larvae were destroyed; in effect, the age of brood at dequeening from which queens emerged was 3.4 days. Apis mellifera / honeybee / queen rearing / development time N '

FACTORS AFFECTING SURVIVAL OF MALLARD DUCKLINGS IN SOUTHERN ONTARIO

Abstract Survival of young is poorly understood, but important to fitness and demographics for many birds. Estimates of duckling survival and the factors influencing it are essential to guiding regional breeding management for ducks. We estimated daily and 30-day duckling survival for Mallards (Anas platyrhynchos) at one of four sites each year during 1997–2000 in southern Ontario, Canada. We examined effects of site-year, brood age, female age, and hatching date on survival. Our best model supported additive effects of site-year, brood age, and hatching date. The odds of daily survival were 8.8 times (95% CI: 4.2–18.5) higher for older (>7 days) relative to younger (≤7 days) ducklings and 1.7 times (0.9–3.1) higher for early-hatched (before 1 June) relative to late-hatched (1 June or later) ducklings. When controlling for differences in hatching date, we did not find support for an influence of female age. Mean 30-day duckling survival across sites was 0.40 (range 0.07–0.50). Extremely low survival at on...

Brood sex ratio in the Kentish plover

How and why do the mating opportunities of males and females differ in natural population of animals? Previously we showed that females have higher mating opportunities than males in the Kentish plover Charadrius alexandrinus. Both parents incubate the eggs, and males provide more brood care than females; thus it is not obvious why the females find new mates sooner than the males. In this study we investigated whether the sex-biased mating opportunities stem from biased offspring sex ratios. We determined the sex of newly hatched, precocial chicks using CHD gene markers. Among fully sexed broods, 0.461 6 0.024 (SE) of chicks (454 chicks in 158 broods) were male, and this sex ratio was not significantly different from unity. The proportion of males at hatching decreased significantly over the breeding season, which occurred consistently in all 3 years of the study. Large chicks were more likely to be males than females. Neither parental age nor body size of male and female parents was related to brood sex ratio. We also sexed a number of chicks that were caught after they left their nest (range of estimated ages 0–17 days) and found that the proportion of males increased with brood age. This relationship remained highly significant when controlling statistically for hatching date. As brood size decreased due to mortality after the chicks left their nest, these results suggest that the mortality of daughters was higher than that of the sons shortly after hatching. Taken together, our results show that the female-biased mating opportunities in the Kentish plover are not due to biased brood sex ratio at hatching but, at least in part, are due to female-biased chick mortality soon after hatching. Key words: Charadrius alexandrinus, Kentish plover, mating opportunities, parental care, seasonal trends, sex allocation, sex ratio. [Behav Ecol 15:58–62 (2004)]

Alternative strategies for a father with a small brood: mate, cannibalise or care

Brood cycling, the alternation of periods of courtship and mating activity ("mating phase") with days of full brood care ("parental phase"), and total filial cannibalism, the consumption of all current offspring by a parent, have been interpreted as a response to the conflicting demands faced by parental males during the breeding season. Under the assumption that these two behaviours result from trade-offs among mating, caring and feeding, the strategy adopted by the male should depend on egg number and age. This hypothesis was tested in the scissors-tail sergeant (Abudefduf sexfasciatus), a common tropical damselfish. Observations of undisturbed males and a brood reduction experiment confirmed all theoretical predictions. The shift from the mating to parental phase occurred when an appropriate number of eggs had been obtained. When the brood was reduced on the first day of the parental phase, males often reverted to the mating phase, but never did so if the manipulation occurred on the second or third day. Only broods that were smaller than average were consumed by the parental male. Artificial reduction of the brood increased the incidence of total filial cannibalism, but the probability of cannibalism decreased with brood age.

Adaptive Male Parental Care in the Giant Bullfrog, Pyxicephalus adspersus

Adaptive Male Parental Care in the Giant Bullfrog, Pyxicephalus adspersus

Distraction Displays in Meadow Pipit (Anthus pratensis) Females in Central and Northern Europe

AbstractDistraction displays to a human were studied in the Meadow Pipit (Anthus pratensis) females in Central (Jeseníky Mountains–Czech Republic; 50°N 17°E) and Northern European mountains (Tydal area–Central Norway; 63°N 12°E) between 1995 and 1998. Three risk‐dependent variables were scored and we found that flushing and settling distances of pipit females decreased with increasing intensity of display both in the Central and the Northern Europe locations. Parental risk taking did not markedly differ between studied populations, although, in particular, larger brood size and reduced opportunity to re‐nest should contribute to a higher intensity of nest defence in the Northern than in the Central European mountains. Moreover, the level of risk taken was not significantly dependent on the air temperature, age of brood and brood size in both study areas, when compared separately. These results do not support the findings of most previous studies on nest defence in birds. Possible causes of our contradictory results are discussed with respect to the reproductive value and the feedback hypotheses.