Population specific annual cycles and migration strategies in a leap-frog migrant

A common migratory pattern in birds is that northerly breeding populations migrate to more southerly non-breeding sites compared to southerly breeding populations (leap-frog migration). Not only do populations experience differences in migration distances, but also different environmental conditions, which may vary spatiotemporally within their annual cycles, creating distinctive selective pressures and migratory strategies. Information about such adaptations is important to understand migratory drivers and evolution of migration patterns. We use light-level geolocators and citizen science data on regional spring arrivals to compare two populations of common ringed plover Charadrius hiaticula breeding at different latitudes. We (1) describe and characterize the annual cycles and (2) test predictions regarding speed and timing of migration. The northern breeding population (NBP) wintered in Africa and the southern (SBP) mainly in Europe. The annual cycles were shifted temporally so that the NBP was always later in all stages. The SBP spent more than twice as long time in the breeding area, but there was no difference in winter. The NBP spent more time on migration in general. Spring migration speed was lower in the SBP compared to autumn speed of both populations, and there was no difference in autumn and spring speed in the NBP. We also found a larger variation in spring arrival times across years in the SBP. This suggests that a complex interaction of population specific timing and variation of breeding onset, length of breeding season, and proximity to the breeding area shape the annual cycle and migratory strategies. Significance statement Migration distance, climate, and the resulting composition of the annual cycle are expected to influence migration strategies and timing in birds. Testing theories regarding migration behaviours are challenging, and intraspecific comparisons over the full annual cycle are still rare. Here we compare the spatiotemporal distributions of two latitudinally separated populations of common ringed plovers using light-level geolocators. We found that there was a larger long-term variation in first arrival dates and that migration speed was slower only in spring in a temperate, short-distance migratory population, compared to an Arctic, long-distance migratory population. This suggests that a complex interaction of population specific timing and variation of breeding onset, length of breeding season and proximity to the breeding area shape the annual cycle and migratory behaviours.

Landscape- and local- level variables affect monarchs in Midwest grasslands

Context It is estimated that over one billion milkweed stems need to be restored to sustain the eastern North American migratory population of monarch butterflies; where and in what context the stems should be placed on the landscape is key to addressing habitat deficits. Objectives We assessed how the amount of appropriate habitat surrounding a particular patch of monarch habitat affects monarch presence and reproduction. To ensure that habitat restoration efforts are targeted towards areas that maximize monarch population growth, it is important to understand the effects of landscape heterogeneity on monarch occurrence in habitat patches (i.e. grasslands with milkweeds) across the landscape. Methods Over two summers (2018-2019), we surveyed monarch adults, larvae, and eggs at sixty grassland sites in Wisconsin that varied in patch size and landscape context (proportion grassland, forest edge density, and road density). We also estimated milkweed density and floral richness to characterize local patch quality. Results Adult monarch abundance was highest at patches with the lowest proportion of surrounding grassland and lowest road density, and was heavily influenced by patch quality variables. Egg and larva density in a patch increased with milkweed density and floral richness within a patch. Patch size was unrelated to monarch abundance. Conclusions These results suggest that optimal sites for monarch habitat restoration are within landscapes with less surrounding habitat and that high milkweed density and floral richness should be conservation goals.

Paternal effects in the initiation of migratory behaviour in birds

What determines why some birds migrate and others do not? This question is fundamental to understanding how migratory systems are responding to environmental changes, but the causes of individual migratory behaviours have proven difficult to isolate. We show that, in a partially migratory population of Eurasian oystercatchers (Haematopus ostralegus), the migratory behaviour of progeny follows paternal but not maternal behaviour, and is unrelated to timing of hatching or fledging. These findings highlight the key role of social interactions in shaping the migratory behaviour of new generations, and thus the spatio-temporal distribution of migratory populations.

Absolute and relative abundance estimates of Australian east coast humpback whales (Megaptera novaeangliae)

The humpback whales that migrate along the east coast of Australia were hunted to near-extinction in the 1950s and early 1960s. Two independentseries of land-based surveys conducted over the last 25 years during the whales’ northward migration along the Australian coastline havedemonstrated a rapid increase in the size of the population. In 2004 we conducted a survey of the migratory population as a continuation of theseseries of surveys. Two methods of data analysis were used in line with the previous surveys, both for calculation of absolute and relative abundance.We consider the best estimates for 2004 to be 7,090±660 (95% CI) whales with an annual rate of increase of 10.6±0.5% (95% CI) for 1987–2004.The rate of increase agrees with those previously obtained for this population and demonstrates the continuation of a strong post-exploitationrecovery. While there are still some uncertainties concerning the absolute abundance estimate and structure of this population, the rate of annualincrease should be independent of these and highly robust.

A STUDY ON MIGRATORY POPULATION IN INDIA: SOME SELECTED STATES

India is the motherland of diverse culture, beliefs and traditions. Indians have lived through ages with the maxim “Unity in Diversity”. In this so varied nature of population, migrations intra-state and inter-state, as well as, international from bordering countries have affected the characteristics of the inhabitants. In this study, we are aiming to assess the nature of population India has, both in rural and urban categories and how these two categories of population are correlated with each other and try to analyze factors which create an impact on the character of the population. We have selected four states, namely, Gujarat, Maharashtra, Bihar and West Bengal for the purpose of our learning.