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Purpose Despite the recent trend of cochlear implantation (CI) at the age of six or even four months is prevalent in many centers around the world, clinicians should be cautious because perinatal risk factors of auditory neuropathy and/or delayed maturation carry the possibility of reversible hearing loss, yielding better auditory performance at the age of one year. The purpose of this study is to raise awareness that early CI may not be universal for all patients. In addition, we specify the factors to be considered in the pre-operative evaluation of CI in infants younger than one year. Methods and results This study describes four cases provisionally diagnosed with severe to profound sensorineural hearing loss that were presented to the CI clinic to determine candidacy for implantation. Two cases had histories of prematurity, one had Down syndrome, and one had a family history of hearing loss. None of the study cases were candidates for CI, as they had varying degrees of hearing improvement. Conclusion Although early CI may yield better auditory performance, the final diagnosis should be made only after repeated subjective and objective measurements as well as family feedback on the child's auditory performance, especially in preterm children. Early auditory brainstem response (ABR) prior to the age of one year in children with cognitive, neurologic, or developmental comorbidities should be interpreted with caution, as ABR \"alone\" could not accurately represent the child's true hearing ability in this patient population.

Age‐related changes in the production of sexually selected assessment signals have been identified across a diverse range of taxa, and in some cases, these changes have been shown to affect receiver response to those signals. One important type of change occurs even after a signaler reaches breeding age, a phenomenon known as delayed maturation. Delayed maturation has been observed in the songs of several bird species, with potential fitness consequences for males as a byproduct of female choosiness or male competition. Here, we analyzed songs recorded across the first three years of life in a cohort of hand‐reared song sparrows Melospiza melodia to detect early‐life age‐related changes in song. We focused on three measures of song complexity, including within song type variation, the average number of notes and the number of unique note types for the most common variant of each song type, and five measures of song production patterns, including singing rate, time interval between songs within a bout of the same song type, time interval between bouts (i.e. when the song type changes), within‐song stereotypy and between‐song consistency. All measures of song complexity and most measures of song production patterns (excluding within‐song stereotypy) changed significantly within individuals as birds aged from one to two years as well as from one to three years (excluding within‐bout time interval), whereas no significant changes occurred from two to three years of age. Based on these features, a linear discriminant model could distinguish between the song of young (age 1) and older (age 2 and 3) adult males, providing support that song could serve as an indicator of age in this species. We discuss potential implications of these results for mate choice and male–male competition in song sparrows.

Quantifying long-term, low reproductive metrics indicative of an ungulate population’s low nutritional status can help spur action to manage for moderate densities in contrast to unsustainable, high densities. We previously ranked the moose (Alces alces gigas) population described here as having the lowest nutritional status among 14 moose populations in Alaska, USA, primarily using reproductive indices (1996– 2005) frommoose with ages estimated by counting cementum annuli. Here, we detailed lifetime reproductive metrics from a subset of known-age female moose initially radio-collared at 9–10 months of age (7 cohorts; 1996–2002); we renewed radio-collars as necessary. We radio-tracked and circled these moose via aircraft at 24- or 48-hour intervals to detect the presence of newborns during the 1998–2018 calving seasons, with meaningful annual sample sizes during 2000–2014. The number of snow-free days in the year preceding parturition had a subtle positive effect on parturition probability, but we found no evidence for effects of the preceding February and March immobilization, cohort affiliation, or the preceding winter’s snow cover on the probability of a female being parturient. The probability of twinning declined as the calving season progressed. Compared with moose production in populations with improved nutrition, our study population experienced low production primarily as a result of delayed maturation, occasional pauses in reproduction, and low twinning rates. Reproductive senescence occurred at normal advanced ages despite nutritional stress. We recorded a 28% parturition rate among 144 females 3 years of age (min. age of reproduction). Parturition rates were stable from 4 to 13 years of age (x̄ = 77%), declined at 14 years of age, and peaked at 15 years of age. Females first twinned at 5 years of age (5%), and the twinning rate increased with age, peaking at 13 years of age (25%). Overall, 136 radio-collared females with complete reproductive histories produced a mean of 5.3 calves/lifetime while being monitored a mean of 7.1 years at ages ≥3 years, although variability in individual production was high. Delaying or pausing reproduction increased the parturition rate at 4 and 5 years of age. However, females that delayed first reproduction produced fewer calves/lifetime on average compared with moose that first produced at 3 years of age. Virtually all moose regularly gave birth with occasional 1-year pauses that acted to enhance production the subsequent year; the incidence of 2 consecutive nonparturient years was 2.8% (24/844). Moose experienced relatively stable, low nutritional status during 2000–2014 based upon low population-wide twinning rates from annual aerial transect surveys (no telemetry) flown a few days after the median annual calving dates. Detailed understanding of low reproductive metrics encouraged empowered stakeholders to allow liberal harvests of female moose (2.0–4.4% of prehunt moose population numbers) and encouraged land managers to allow wildfires to burn 25% of the study area to improve moose carrying capacity. We helped manage a 31% decline in moose numbers during 2004–2012 by implementing liberal harvests of female moose. Elevated population-wide twinning rates in 2012, 2015, 2017, and 2018, similar to elevated levels prior to 1997, were likely a positive response to lower moose densities and improved browse after wildfires.

Many animals use multiple signals in sexual communication, but our understanding of the interactions between multiple signals, particularly in inexperienced breeders, is limited. In birds, delayed plumage maturation (DPM) is well documented; young birds appear duller than adults, despite reaching sexual maturity. Age-related changes in song structure are also common in songbirds, though the extent to which songs of yearling males differ from those of adults (delayed song maturation, DSM) and its prevalence in species with DPM is unknown. We tested for DSM in the mate-attraction (repeat) song of a species with dramatic DPM, the American redstart (Setophaga ruticilla). Repeat song structure of territorial yearling and adult males differed significantly, based on discriminant analysis of nine non-collinear song features. Combined with previous evidence of delayed maturation in territorial (serial) song, we provide the first evidence for DSM in different song types used in different behavioral contexts during the breeding season of a migratory songbird. Within adults, variation in repeat song was associated with pairing, earlier onset of breeding, and number of offspring sired, suggesting a potential benefit for expressing more adult-like song. We found no relationship between the expression of adult-like repeat song and plumage in either age class. These results indicate that delayed maturation of repeat song in yearling redstarts is not due to a generalized delay in signal development, and suggest further work is needed to determine whether mate attraction (for both yearling and adult males) provides greater pressure to sound more \"adult-like\" than to look more \"adult-like\".

Age-dependent breeding performance is arguably one of the best-documented phenomena in ornithology. The existence of age-related trends has major implications for life-history theory, but the proximate reasons for these patterns remain poorly understood. It has been proposed that poor breeding performance of young individuals might reflect lack of foraging skills. We investigated this possibility in a medium-sized, powerful raptor-the northern goshawk Accipiter gentilis. Male goshawks are responsible for providing their females and their offspring with food. We hypothesized that young males may generally show poor breeding performance or even delay breeding, because they lack the experience to hunt efficiently-especially, their principal avian prey, the feral pigeon Columba livia. Our study exploited a rare 'natural experiment', the expansion phase of an urban population, where intraspecific interference was negligible and many young males bred successfully. This enabled us to examine the improvement of foraging skills in a larger sample of young individuals, and in more controlled conditions than usually possible. Using data from individually identified male breeders, we show that, consistent with our hypothesis, the proportion of pigeons in the diet increased significantly with male age, for at least the first three years of life. Other studies have shown a parallel increase in productivity, and a positive effect of a pigeon-rich diet on brood size and nestling condition, stressing the potential fitness relevance of this prey species for goshawks. Our results suggest a causal link between patterns of age-dependence in foraging ecology and reproductive performance. Furthermore, our study is, to our knowledge, the first demonstration that prey choice of breeders, which might reflect individual hunting skills, is age-dependent in a raptor.

Multiple raptors show juvenile plumage that is substantially different from that of their parents. Here, we test the prediction that the colouration of the juvenile northern goshawk Accipiter gentilis resembling the colouration of the common buzzard Buteo buteo acts as a form of aggressive mimicry. The goshawk specialises in hunting larger birds and mammals up to the size of geese or hares, while the buzzard preys mostly on small rodents. Larger birds may thus consider juvenile goshawks as less dangerous raptors, and the juvenile goshawk may thus gain an advantage when hunting. We used the Eurasian magpie Pica pica, a common prey of the goshawk, to test this prediction. We compared the behavioural responses of magpie parents defending their freshly fledged young towards mounts of an adult goshawk, juvenile goshawk, and buzzard. To be able to assess whether this behaviour differs from responses to a nest predator and a harmless bird we also presented a common raven Corvus corax and common pheasant Phasianus colchicus as baseline stimuli. Both juvenile and adult goshawks elicited antipredatory behaviour, but magpies took more risks facing juvenile goshawks. Additionally, the intensity of antipredatory behaviour towards the juvenile goshawk was also higher than towards the buzzard. We thus conclude that magpies do distinguish between juvenile and adult goshawks, as well as they do distinguish juvenile goshawks from buzzards. They are able to assess the threat particular raptors represent and respond accordingly. Analysis of spectral reflectance of stuffed specimens of these three raptors suggests there are differences, which can be used for the appropriate recognition. In conclusion, we cannot confirm the hypothesis of aggressive mimicry in juvenile goshawks that interact with magpies.

Only males (fully mature and failing to mature) and intersexes have been found among triploids of pink salmon. Possible mechanisms of genetic sex determination in pink salmon are discussed. The possibility of using triploids to regulate sizes of artificial pink salmon populations is also discussed. Triploids of pink salmon are deemed inefficient to use in aquaculture. Delayed maturation is observed in some diploid females reared in farming cages.

Purpose The research aimed to investigate the average age of recovery in infants with delayed visual maturation (DVM). DVM is diagnosed retrospectively and there are currently no management guidelines. This study gives an evidence-based recovery time which can help clinicians to appropriately reassure anxious parents about DVM prognosis. This research is significant as this is the largest participant study about DVM to date. Method This is a retrospective service evaluation of 50 infants with DVM presenting to St James University Hospital between 2012 and 2017. The DVM was classified into either type I or type II. Several key variables were recorded including: patient gender, age at recovery, type of DVM and whether Electrodiagnostic testing was used. Results STATA analysis showed that the average age of recovery for type I and type II DVM was 6.708 and 13.464 months, respectively. A multivariable linear regression adjusted for gender as a confounder. The average age of recovery was 6.179 months longer for infants with type II DVM which is a statistically significant difference (95% CI: 3.214–9.143, P value: < 0.001). Conclusion This research supports the hypothesis that the age of recovery in type I DVM is significantly shorter than type II when adjusted for gender. The main limitation is that recovery age is recorded from when the infants attended clinic, however; their vision could have recovered prior to this. In the future, additional multi-centre research needs to be conducted looking at larger patient samples to allow for further sub-categorisation of DVM types.

Song complexity is often regarded as a sexually selected trait that reflects the overall quality of a male. In many passerine species, old males possess larger song repertoires than younger males. This may be either because individual males improve their performance as they get older (longitudinal increase) or because poor singers have reduced viability and, hence, are underrepresented in old age classes (cross-sectional increase). We studied the age dependence of repertoire size and other song traits in a German and a Swedish great reed warbler (Acrocephalus arundinaceus) population. We found marked differences between longitudinal and cross-sectional approaches, as well as between the two study populations. In the German population, we found that syllable switching, a measure of immediate versatility and strophe length, increased with age in a cross-sectional analysis. This was not because birds improved with age (longitudinally) but because syllable switching was positively correlated with male longevity. However, in Sweden, syllable switching seemed to be unrelated to age and longevity. In the Swedish population, individual males increased their repertoire size as they got older (longitudinal increase), but this did not happen in the German population. Hence, two populations, even when belonging to the same subspecies, may differ in whether or not they show delayed song maturation.

Preterm infants often require oxygen supplementation, resulting in high risk for bronchopulmonary dysplasia (BPD) and neurodevelopmental deficits. Despite a growing number of studies, there is still little knowledge about brain injury in BPD models. Therefore, we exposed neonatal C57BL/6 mice to 85% oxygen from birth to postnatal day (P) 14. At P28, two weeks after recovery under normoxic conditions, right hemisphere was used for the analysis of mRNA and the left hemisphere for protein expression of neuronal cells, neuroinflammatory and vascularisation markers, analysed by real-time PCR and Western blot, respectively. Hyperoxia led to an altered expression of markers associated with neuronal and oligodendrocyte maturation and neuroinflammation such as Dcx, Nestin, Il-1β, Il-6, NG2, and YM1/2. These changes were accompanied by an increased expression of genes involved in angiogenesis and vascular remodelling, e.g., Vegf-a, Nrp-1, and Icam-1. Together, 14 days of hyperoxia triggered a phenotypic response, resembling signs of encephalopathy of prematurity (EoP).