Keita D. Tanaka

A colour to birds and to humans: why is it so different?

The avian visual model has become nowadays a standard for quantifying colours of birds. Here, I review the biological bases of the importance of visual modelling to most ornithologists, focusing on the causes of the difference in colours to birds and to humans, both proximately and ultimately. Not only the sensitivity of retinal photoreceptors and performances of ocular media, but also the number of photoreceptor types are all attributed to the bird–human difference proximately. As the ultimate cause, the evolutionary history of birds and humans should divide the colours perceived by them: birds would retain their colour vision from the ancient ancestry, while primates such as humans would have reacquired the colour vision relatively recently. Finally, I review how to process and to analyze data produced by the visual model.

Maternal provisioning and possible joint breeding in the burrower bug Adomerus triguttulus (Heteroptera: Cydnidae)

Subsocial burrower bugs (Heteroptera: Cydnidae) provide unique opportunities to investigate evolutionary ecological questions regarding parental provisioning and family dynamics. Observations and marked nutlet‐setting experiments in the field showed that Adomerus triguttulus females progressively delivered mint nutlets into nests harbouring nymphs under the litter. More than one female often attended nymphs, but not eggs, in a nest in the field. The number of nymphs aggregating in a nest with a single female was usually smaller than that in a nest with two females, suggesting the joining of different families and facultative joint parental care. There was a positive correlation between the number of nutlets delivered and the number of nymphs in a nest. The number of attendant females also affected the amount of provisioning; more nutlets were found for second‐instar broods with more females. The effect of brood size on provisioning was confirmed for families under laboratory rearing. Maternal provisioning also varied with the developmental stage of offspring; second‐instar broods received more nutlets than first‐instar broods, with a temporal decrease in provisioning during the moulting of nymphs. Considering the growing evidence of food solicitation signals of young in subsocial insects, the observed finely tuned supply of food by the female could be induced by begging signals from the nymphs.

Mating system and extra-pair paternity in the Fan-tailed Gerygone Gerygone flavolateralis in relation to parasitism by the Shining Bronze-cuckoo Chalcites lucidus

Extra-pair copulation can increase genetic diversity and offspring fitness. However, it may also increase intra-nest variability in avian hosts of brood parasites, which can decrease the discrimination ability of host parents towards the parasite. In New Caledonia, the Fan-tailed Gerygone (Gerygone flavolateralis), which is parasitized by the Shining Bronze-cuckoo (Chalcites lucidus), has two nestling morphs, dark and bright, that can occur in monomorphic and polymorphic broods. Gerygone parents recognize and eject parasite nestlings from their nest, but the presence of polymorphic broods may increase the chances of recognition errors. Using 17 microsatellite markers, we investigated the mating system of the Fan-tailed Gerygone to understand the mechanisms underlying nestling polymorphism. We hypothesised that extra-pair copulations would lead to a higher proportion of polymorphic broods caused by higher genetic variability, thus creating a trade-off between genetic benefits and host defence reliability. Extra-pair paternity occurred in 6 of 36 broods, which resulted in 6 of 69 offspring sired by extra-pair males. Broods with and without mixed paternity were comparably often parasitized. Extra-pair paternity did not influence the proportions of bright, dark and polymorphic broods. Compared to bright siblings in polymorphic broods, dark nestlings tended to have lower heterozygosity, particularly in loci associated with skin coloration. The results also suggested that there is no obstacle for genetic exchange between individuals from forest and savannah, possibly due to dispersal of offspring. We conclude that the Fan-tailed Gerygone is a socially monogamous species with a low rate of extra-pair paternity compared to closely related species. Extra-pair paternity increased offspring genetic variability without measurable associated costs by brood parasitism. The results highlight the importance of studying host mating systems to assess the trade-offs between host defence and offspring fitness in co-evolutionary arms races.

Establishment of Microsatellite Markers to Assess the Mating System of the Fan-Tailed Gerygone (Gerygone flavolateralis) for Studying Cuckoo-Host Arms Race

We developed a set of microsatellite markers for the fan-tailed gerygone (Gerygone flavolateralis), host of a brood parasite, the shining bronze-cuckoo (Chalcites lucidus). We used 454 pyro-sequencing to establish 17 polymorphic microsatellite markers. The number of alleles per locus ranged from 6 to 18, the expected heterozygosity from 0.328 to 0.931 and the polymorphism information content from 0.306 to 0.916. The developed set of microsatellites will allow us to determine the gerygones mating system, which is crucial to understand inheritance of dichromatism in skin colour of their chicks.

Gourmand New Caledonian crows munch rare escargots by dropping

Numerous broken shells of a rare endemic snail Placostylus fibratus, a species rated as vulnerable, were scattered around rocky beds of dry creeks in rainforest of New Caledonian. We set a video camera near one site to identify the predator. We recorded a New Caledonian crow Corvus moneduloides dropping and consuming the snail. This is the first direct evidence of the crow dropping of this native species. The assumed weight of snails relative to the crow is exceptionally heavy among prey dropped by birds.

Signal exploitation by parasitic young in birds: a new categorization of manipulative signals

ABSTRACT Many studies revealed that parasitic young mostly emit signals that are used in parent-offspring communication of hosts, but sometimes not. The terms used to explain host manipulation signals are not unified, then presenting confusion. Here we propose a new categorization of signals used for parasitic manipulation. Host manipulative signals could roughly be divided into two patterns according whether a parasite exploits signals actually used in parent-offspring communication of hosts (signal exploitation) or not (sensory exploitation), in relation to particular selective pressures that parasites face, such as nestling discrimination by hosts or deficient stimulation by parasites to obtain sufficient food.

Impact of inability to turn in bed assessed by a wearable three-axis accelerometer on patients with Parkinson's disease

Background Difficulty turning over in bed is a common night-time symptom in Parkinson’s disease (PD). We aimed to quantitatively evaluate overnight turnover movements using a three-axis accelerometer and to investigate whether inability to turn in bed is related to daytime sleepiness, sleep quality, and depressive mood in PD patients. Methods We examined 64 patients with PD (mean age, 73.3±8.21 years; modified Hoehn-Yahr [mH-Y] stage, 3.0±1.0; disease duration, 7.2±6.3 years; unified Parkinsons disease rating scale [UPDRS], 36.9±18.3). Overnight monitoring of turnover movements using a wearable three-axis accelerometer was performed in all patients. Nocturnal kinetic parameters including total time recumbent, total time supine, number of turnover movements, and mean interval between turnover movements were obtained. Daytime immobility was assessed using the Barthel index (B-I), UPDRS, and mH-Y stage. Patients were also assessed with the Epworth Sleepiness Scale (ESS), Parkinson’s Disease Sleep Scale-2 (PDSS-2), and Beck Depression Inventory (BDI). Results Number of turnover movements in bed correlated negatively with disease duration (r = -0.305; p<0.05), L-dopa-equivalent dose (r = -0.281; p<0.05), mH-Y staging (r = -0.336; p<0.01), total score of UPDRS (r = -0.386; p<0.01) and positively with B-I score (r = 0.365; p<0.01). Number of turnover movements in bed was generally inconsistent with awareness of turnover movement impairment as evaluated by PDSS-2 Item 9 scores, but patients who were never aware of impaired turnover movements showed ≥5 turnover movements overnight. Multivariate logistic regression analyses revealed no correlations between number of nocturnal turnover movements in bed and BDI, ESS, or PDSS-2. Use of anti-psychotic drugs was associated with ESS (p = 0.045). UPDRS was associated with PDSS-2 (p = 0.016). Conclusion Decreased number of turnover movements may not be a direct determinant of daytime sleepiness, sleep disorders, or depressive mood in PD patients. Use of anti-psychotic drugs and higher UPDRS score are factors significantly associated with daytime sleepiness and uncomfortable sleep, respectively.