Scholars agree that changes in vegetation have been influencing population sizes of ground-foraging songbirds in Dutch dune grasslands. Due to a lack of knowledge concerning the breeding biology of these species, the mechanisms linking vegetation change and population development remain unclear. Here, I describe the breeding biology of three co-occurring insectivores in Dutch dune grasslands: Meadow Pipit Anthus pratensis, European Stonechat Saxicola torquatus and Northern Wheatear Oenanthe oenanthe. The nestling diet of Meadow Pipits contained many dipterans, such as crane flies (Tipulidae), but almost no beetles and relatively few noctuid caterpillars, whereas beetles and noctuid larvae were important in the diets of both European Stonechat and Northern Wheatear nestlings. Mean brood size was smallest in Meadow Pipit and equal in European Stonechat and Northern Wheatear. Nest depredation was similarly high in the open-nesting Meadow Pipit and European Stonechat, resulting in lower nest success compared to Northern Wheatear, a cavity-breeder. Provisioning rate per nestling was highest in Northern Wheatear, the largest species, with no observed differences between Meadow Pipit and European Stonechat, which resulted in higher per brood provisioning rates for European Stonechat. Since the mean brood size of European Stonechat is larger than that of Meadow Pipit, and since nest depredation generally increases with provisioning rates, one would expect a higher depredation rate in European Stonechat. This suggests that differences in nest site selection between Meadow Pipit and European Stonechat result in relatively lower nest depredation rates in European Stonechat and similar nest success to Meadow Pipit. I suggest that future work should focus on how different vegetation types relate to prey abundance, foraging habitat and vegetation-specific nest depredation, in order to better understand the putative relationships between population growth and vegetation in coastal dune grasslands.

Over the past 50 years, the population of Continental Black-tailed Godwits Limosa limosa limosa breeding of the East Atlantic Flyway has been in steep decline. This decline has previously been documented in trend analyses and six Netherlands-wide count-based population estimates, the last of which was completed in 1999. We provide an updated population size estimate and describe inter-annual fluctuations in the population between 2007 and 2015. To generate these estimates, we integrated a mark-recapture survival analysis with estimates of the densities of colour-marked individuals at migratory staging sites with known proportions of Continental and Icelandic L. l. islandica Black-tailed Godwits within a Bayesian framework. The use of these analytical techniques means that, in contrast with earlier efforts, our estimates are accompanied with confidence intervals, allowing us to estimate the population size with known precision. Using additional information on the breeding destination of 43 godwits equipped with satellite transmitters at Iberian staging areas, we found that 87% (75–95% 95% CI) of the nominate subspecies in the East Atlantic Flyway breed in The Netherlands. We estimated that the number of breeding pairs in The Netherlands has declined from 47,000 (38,000–56,000) pairs in 2007 to 33,000 (26,000–41,000) in 2015. Despite a temporary increase in 2010 and 2011, the population declined by an average of 3.7% per year over the entire period from 2007–2015, and by 6.3% from 2011–2015. We conclude that investing in an intensive demographic programme at a regional scale, when combined with targeted resightings of marked individuals elsewhere, can yield population estimates at the flyway scale.

In this study we compare autumn migration strategies in two subspecies of the Common Ringed Plover Charadrius hiaticula in the southern Baltic Sea. This species exhibits a leap-frog migration pattern, whereby northerly breeding populations (C. h. tundrae; henceforth tundrae) migrate past the whole range of the southern population (C. h. hiaticula; henceforth hiaticula). Hiaticula migrates the shortest distance and is hypothesised to minimize energy spent on migration, whereas tundrae is hypothesized to minimize time, because a longer migration imposes time constraints upon other stages of a migrant's life history, such as moult and breeding. We use biometric data collected at Ottenby Bird Observatory, southern Öland, Sweden, between 1946–2012, to test whether each subspecies demonstrates characteristics associated with either an energy- or time-minimized migration. We used the decline in wing and total-head length over the season to distinguish the subspecies. Hiaticula migrated earlier in the season (July—mid August) compared to tundrae (late July—late September). Also the relative timing of age groups between the two subspecies differed. Juvenile and adult hiaticula migrated synchronized in time, whereas tundrae had two main periods of passage for adults (earlier) and juveniles (later). The timing fits that of other studies and gives complementary information about the passage in Europe. Juvenile tundrae showed a positive trend of observed fuel loads as the season progressed, whereas the other groups did not. Daily fuelling rates within the same season were low compared to other wader species that use Ottenby as a stopover and no difference between subspecies was found. However, tundrae stopped over for a shorter time compared with hiaticula. There was no difference in average migration speed between the subspecies, although tundrae had a higher maximum speed. There was large variation in yearly numbers between age classes in the two subspecies. In hiaticula the yearly average was 8 adults and 37 juveniles. The ratio of juvenile to adult tundrae on the other hand was almost 1:1, indicating equal use of Ottenby as stop over site in autumn. No trends in observed fuel loads over the season in hiaticula are consistent with an energy minimizing migration. As for tundrae, a shorter stopover time compared to hiaticula and a positive relationship between observed fuel load and time, are consistent with time minimizing migration. However, there are many uncertainties and more studies of migratory behaviours at several sites along the migration route are needed to understand the differences in migration strategies in this species.

The population of Black Terns in The Netherlands strongly declined in the period from 1950 to 1980. In recent years numbers have been more stable. The supply of artificial nest platforms has successfully attracted breeding Black Terns, and 80% now breed on platforms. In this paper we describe the development in numbers and breeding success of a Black Tern population in The Netherlands over the period 1982–2015, where ample nest platforms have been supplied over time. Using this database we question whether we can increase the breeding population by supplying platforms. We are uncertain whether tern numbers responded to an increase in nest platforms, or whether researchers responded to an increase in tern numbers by putting out more nest platforms. We analyse (1) settlement and breeding success in relation to nesting substrate, (2) the covariation between breeding numbers and platform numbers over time and space, and (3) the density dependence of settlement and breeding success. Against this background we analyse whether the annual change in platform numbers is followed by a change in tern numbers, as would be expected if there was a causal link between the two. We show that in our study area reproduction on artificial platforms was higher than on natural substrate and that the tern population in the whole study area increased over the study period. This increase in numbers was associated with an increase in the number of platforms, as expected when platforms affect tern numbers. Settlement in the first year after introduction of the platforms was higher, but in later years there was no correlation between annual change in the number of platforms and annual change in the number of breeding pairs. We did not detect a decline in the number of fledglings produced per pair with increasing tern breeding density. In conclusion, although the general pattern suggests positive effects of platform numbers on tern numbers, we are strictly speaking not able to show that supplying nest platforms caused the increase in the local Black Tern population over the study period. The answer awaits large scale experiments with control areas and individually marked birds to quantify survival and dispersal.

The Sand Martin Riparia riparia is a trans-Saharan migrant species, whose populations are declining throughout Europe. We present the results of a multiple year study on a breeding population of Sand Martins along the River Po in Northern Italy through ringing breeding birds at nesting colonies (2002–2014). There was a trend for the abundance of the studied population to fluctuate. Recapture data were analysed to obtain apparent survival probabilities which differed between the sexes, but not between years. No apparent relationship was found between survival and three different meteo-climatic indices (North Atlantic Oscillation, Sahel rainfall and Lake Chad rainfall). During the 1980s and 1990s, winter survival was positively correlated with rainfall in the winter quarters. Although rainfall in the winter quarters has been more stable during the past 15 years, Sand Martin populations are still decreasing. Our findings suggest that the relationship with rainfall no longer holds, and that current population declines may be unrelated to climate in the winter quarters.

In 2011 and 2012 the breeding success of Red-billed Tropicbirds Phaethon aethereus mesonauta was monitored on Saba, a 13-km² island in the Caribbean Netherlands. The two colonies on the south and south-west side of the island both contain approximately 100–300 nests; breeding success was zero at these sites, due to predation of newly hatched chicks by Feral House Cats. In the single large colony of Old Booby Hill (estimated to contain approximately 1000 nests) on the east side of the island, rates of predation were lower, resulting in a breeding success (survival from laying until fledging, as far as observed) of 65%. Calculations of daily survival of eggs and chicks following Mayfield, resulted in a nesting success of 48% per pair. I conservatively estimated the size of the Saba breeding population to be at least 1300–1500 pairs, which is larger than the previous estimate of 750–1000 pairs. Potentially, the number of breeding pairs may be as high as 1850 pairs.

Food availability and diet are two key issues in understanding the ecological requirements of a migratory species in stopover sites and in taking effective conservation measures. In the case of the globally threatened Aquatic Warbler, there have previously been no studies examining diet selection in the Iberian Peninsula, a key region for their post-nuptial movements. In this context, the availability of arthropods in different habitats (reeds, rushes and grassland), the composition and biomass of prey in faecal samples, and diet selection were all investigated in a wetland in northwest Spain. The results showed a higher total abundance of arthropods in grassland and rushes: habitats which were more similar to each other, in terms of vegetation physiognomy and composition of invertebrates, compared with reeds. In terms of prey abundance, diet was dominated by Araneae, Heteroptera and Homoptera. However, the groups that contributed most to the ingested biomass were Diptera (Tipulidae), Odonata and Orthoptera, followed by Araneae. Prey selection indices showed a preference for these groups, which all contain insects with a large body length. These diet characteristics showed many similarities with studies in other stopover and breeding areas, but differ in that Araneae were the main arthropod prey at this stopover site.

Partial incubation refers to short bouts of incubation during the egg laying period. I determined the occurrence of partial incubation and its association with the number of eggs in the nest at its onset, in the Blackcap Sylvia atricapilla. Additionally, I studied the relationships between the occurrence of partial incubation at a given number of eggs, air temperature and time of day. At each stage of egg-laying, two nest checks were done each day to establish if the clutch was incubated, until 5 eggs were laid; in this study, a clutch of five was a complete clutch. Incubation of one-, two-, three- and four-egg clutches was observed in 0.0%, 34.2%, 72.2% and 95.8%of the nest checks, respectively. Of the two daily checks, incubation was observed only once in 51.8%, 37.0% and 8.3% of two-, three- and four-egg clutches, respectively, for nests with confirmed incubation. There was no relationship between either air temperature or the time of the nest check and whether or not a clutch was incubated. A significant increase in temperature of the eggs occurred only after the fourth egg was laid.