Extra-pair paternity in a species with frequent extra-pair courtship feedings, few extra-pair copulations, and male-biased parental care

Patterns of extra pair paternity (EPP) and intraspecific brood parasitism (IBP) were studied in a Whiskered Tern Chlidonias hybrida population characterized by female brood desertion, a high level of extra pair courtship feedings (10%) and a low level of extra pair copulation (EPC; 0.6%). In this study, we used a set of microsatellite loci to analyse parentage in 56 Whiskered Tern families from southern Poland. Depending on the method, we detected that 1.4%–3.6% of chicks were sired by an extra-pair male, and extra-pair chicks were present in 3.6%–8.9% of broods. IBP was observed in 8.9%–14.3% of broods, corresponding to 3.6%–6.4% of the chicks. The low rate of EPP is in agreement with the hypothesis that in species with high male parental investment, females should avoid EPC. The low level of IBP indicates that intraspecific egg dumping is not a common female strategy in Whiskered Tern, similar to many other colonial waterbird species.

Birds and birding 2013-2020 at Macaneta, Southern Mozambique

The Macaneta area lies in the Incomati River estuary in northern Maputo Bay, Maputo Province, southern Mozambique. The 56 km2 area of study was selected based on access from tracks and follows no formal boundaries. The site comprises a 10 km stretch of ocean beach, coastal dunes with patchy thicket forest, and low lying wet grasslands inland to the Incomati River. The wetlands have complex hydrology offering diverse salinity and temporal conditions. The peninsula of Praia de Macaneta is also included in the study site but with few data. Improved access to the site in Oct 2016 enabled over 200 field ornithological visits Oct 2016-Oct 2020 and the sightings are analysed and reported herein. A total of 295 species was recorded including eight Globally Threatened birds (three Endangered, five Near-threatened) and Internationally Important numbers of White-breasted Cormorant Phalacrocorax carbo and Whiskered Terns Chlidonias hybrida were found. Three new birds for Mozambique were discovered; Sharp-tailed Sandpiper Calidris acuminata (first for Africa), White-rumped Sandpiper C. fuscicollis and Pearl-breasted Swallow Hirundo dimidiate. An annotated checklist of selected species is presented. The Sharp-tailed Sandpiper in particular drew much birder interest with 254 international visitor days over the 12 weeks of its first visit Feb-Apr 2018, contributing over US$12,000 into the local economy. The bird returned for two further seasons but it was not possible to gather further data.

Sex-specific growth of nestlings of the Whiskered Tern Chlidonias hybrida, a species with sexual size dimorphism and female brood desertion

The growth of a nestling during the first few weeks after hatching is crucial for its further life and is sensitive to the conditions experienced during this period. Among species exhibiting Sexual Size Dimorphism (SSD), one of the most important factors influencing growth parameters is the sex of the hatchlings. In this study, we tested whether sex and other factors (hatching date, egg volume, brood size and sex ratio in the brood) were related to sex on growth parameters in Whiskered Tern (Chlidonias hybrida) chicks. In this species, males are 3%–10% larger than females when adult. At hatching, only the total head length was greater in males than females, but values close to fledging were greater for most of the measured parameters (3%—tarsus, 4%—total head length, 13%—body mass). Moreover, the maximum body mass growth rate was higher in males but females entered the rapid growth phase somewhat earlier and achieved the final total head length sooner. Nestling growth was also significantly correlated with brood size and hatching date, though mostly negatively (e.g. lower tarsus and total head length asymptote, lower maximum growth rate and growth rate constant of total head length in bigger and later clutches). The occurrence of SSD during the nestling period and higher maximum growth rate of body mass in males indicates that the costs of raising sons may be higher than of raising daughters. However, we did not find evidence of either sex-biased nestling mortality or skewed sex ratio.

New species on the list of species with intraspecific nest parasitism

Intraspecific nest parasitism has only recently received more attention from ornithologists. In 2001, Yom-Tov published a list of 234 species that had exhibited this behaviour. I have since found literature data on four additional species in which intraspecific nest parasitism has been observed. No such record has so far been published from Hungary. This study presents records on 25 species from Hungary and on one species from Croatia, out of which I have not found any reference for intraspecific nest parasitism in the literature for Cattle Egret (Bubulcus ibis), Eurasian Thick-knee (Burhinus oedicnemus), Black-winged Stilt (Himantopus himantopus), Collared Pratincole (Glareola pratincola), Mediterranean Gull (Larus melanocephalus), Little Tern (Sternula albifrons), Whiskered Tern (Chlidonias hybrida), Eurasian Roller (Coracias garrulus) and Eurasian Jackdaw (Corvus monedula). In addition to records from Hungary, for Black-headed Gull (Larus ridibundus) and Mediterranean Gull I also present observations from Slovakia, and for Common Shelduck (Tadorna tadorna) from Germany.

Reproductive success of Whiskered Tern Chlidonias hybrida in eastern Spain in relation to water level variation

Background A study on the Whiskered Tern Chlidonias hybrida was carried out between 2002 and 2009 in wetlands of eastern Spain to evaluate how water level fluctuation affects its reproductive success (hatching, fledgling and breeding success). This species is catalogued as Vulnerable in Spain and has an unfavorable conservation status in Europe. Methods Our study includes 18 sampling areas from five wetlands, covering a total of 663 nests, 1,618 eggs, 777 nestlings and 225 fledglings. The colonies were visited at least twice per week in breeding period. The number of eggs and/or nestlings present in each nest were annotated each time the colonies were visited with the aim to compare the evolution of these parameters with time. Hatching success was calculated as the proportion of egg that hatched successfully. Fledgling success and breeding success were calculated as the proportion of chicks that fledged successfully and the proportion of eggs that produced fledglings. We used the Kruskal–Wallis test to analyze the differences in the dependent variables hatching, fledgling and breeding success among the wetlands and the sampling areas. We explored the relationship between the different reproductive success with the average fluctuation rate and the anchoring depth of nests, using statistics of the linear regression. Results It was observed that the reproductive success varied significantly in the interaction among the different categories of water level fluctuation and the different areas (using the Kruskal–Wallis test). Our records showed that pronounced variations in water level destroyed several nests, which affected the Whiskered Tern reproductive success. Considering all events that occurred in 18 areas, the mean (±SD) of nests, eggs and nestlings that were lost after water level fluctuations were of 25.60 ± 21.79%, 32.06 ± 27.58% and 31.91 ± 21.28% respectively, also including the effects of rain and predation. Discussion Unfavorable climatic events, such as strong wind, rain or hail, also caused the loss of nests, eggs and nestlings, even when wetland water levels remained constant. The influence of the anchorage depth of the nest and the water level fluctuation rate were analyzed and did not provide statistically significant results. It was not possible to establish a clear pattern on these latter variables, so further studies are needed to obtain more significant results. We propose to undertake similar studies in wetlands where the water level can be regulated, with the range of nest anchorage depth on the emergent vegetation being between 30 and 60 cm, which could improve the reproductive success in this kind of habitats. As recommendation, in water level controlled wetlands (that use sluices), it should not vary more than ±6 cm in a short time (1–2 days) once the nests are established since it negatively affects their reproductive success.