Mysterious bird

History of the Nightjar

Probably it was Aristoteles who described the 'Goatsucker' for the first time around 350 B.C. He was convinced this mysterious bird would attack goats to suck dry their utter. Actually, this was not a bad observation for that time if you know that Nightjars catch moths and beetles during dusk and dawn. So the observation that Aristoteles made probably were Nightjars that were foraging between the grazing goats.

Even today it's hard to see Nightjars. This bird is remarkably well camouflaged. During daytime you can approach them without even noticing it. But at dawn, Nightjars become active. Males display their impressive churring at the edge of clearings and open places. After a few minutes they disappear with short 'kweeks', back into their hidden world.

Many bird species live during daytime. This makes it relatively easy to monitor their behaviour. This is not the case for Nightjars, and that's why even today many questions about this bird remain unsolved. Where do they breed and sleap? Where will they find food, and what do they eat? Which terrains do they need to survive, and how big is their homerange? These questions are hard to solve by 'normal monitoring techniques'. To discover the hidden world of Nightjars, we use radiotelemetry.

Since the end of the 19th century suitable habitat of Nightjars decreased and fragmented very fast. Because of this Nightjars were added to Annex I of the Birds Directive. On the Flemish Red list Nightjars were added to the list of 'vulnerable species' who can change to a 'endangered' status. By exception of some Walonian small populations in Lagland, Spa-Malchamps an Croix-Scaille (50-60 pairs) most Nightjars of Belgium occur on the sandy soils of the Campine area.

After an absolute minimum of only 208-281 pairs in 1980 the population in Flanders seems to be increasing, but population estimates diverge extremely. In the province of Limburg the population is estimated on 500 pairs in 2002 an 800 in 2008. It is really important to interpret these numbers with great cautiousness because these estimates are made based on the number of male churring locations. However, by radiotagging male Nightjars we have discovered that males sometimes have 3 to 5 churring locations in one season. This means the number of pairs presumably is lower than current estimates.


They look like..

Nightjars have a wingspan of 52 - 59cm. When they are flying you can mistakably identify them as a small falcon or cuckoo. They plumage is brown-greyish and is speckled with numerous white and black dots and stripes. Most of the times Nightjars lay on a dark substrate and keep very quiet. Resting on a branch or on the ground, they are really hard to destinguish from the background. When Nightjars are grooming or cleaning, they move like a branch or leaf that is moved by wind.

The remarkable thing about Nightjars is their churring, a long rattling sound with short stops. Most churrings end with an 'errrrurrrruu' or deep stuttering 'fiORRRRR'. In flight they sometimes make shot 'Kweek' sounds. During displays male Nightjars clap their wings above their backs to make clapping sounds.


What and where?

During daytime Nightjars most of the time rest in trees. In this case they seem to prefer the dense crowns of Corsican pines. When night comes, you can hear males churring. They sing from dead branches, just below the top of a high tree at the edge of a clearing. This is the metalic sound you can hear in forest areas.

Early in the evening Nightjars forage in the presence of their sleeping- and breadinglocations. They feed mainly in forest edges or near the tops of trees. After a couple of minutes they leave for their main feeding grounds which are sometimes more than 1-3km away. During breading season Nightjars travel several times per night more than 1-3km to their feeding grounds. They fly to extensive farmlands in river valleys to forage. Presumably these areas hold more food for Nightjars than bare heath or dune areas. When dusk breaks, Nightjars return to their sleeping- or breading sites to rest during daytime.


The world in Belgium

In Flanders, you can find Nightjars manly on sandy soils in the Campine region. There are some small populations in heath-fragments in the southern part of Belgium . Nightjars are inhabitants of forest edges. You can find them in transitions between forest and open heath- or dune areas. Nesting sites of Nightjars are manly found some meters inside a forest edge. Here they look for coverage of some low trees to protect them from predators. Because Nightjars make their nests close to open areas and walking trails, they are especially vulnurable for disturbance by dogs. So please keep your dogs close to you!

Nightjars forage for food in a diverse landscape of trees, shrub, forest edges and extensive farmlands. There areas are particularly rich in food because they cool down very slow. Our studies show that Nightjars avoid large open areas with intensive farmlands. This is probably because of the lack of food or coverage against predators.


Where do they go?

Nightjars are migratory birds that visit our regions for only a few months a year. They arrive late May and leave at the end of August. During this short stay they try to complete two breedings. Nightjars lay 2 white eggs, with brown-blackish dots, on bare ground. When there is a period of bad weather in the beginning of the breeding season, Nightjars may delay their first breading. When they do this, there is not enough time to complete a second brood.