Nocturnal songbird surveys have been conducted in Estonia since 1991. According to Jaanus Elts, coordinator of the Estonian Ornithological Society's nocturnal songbird census, the survey began at a time when various bird-monitoring methods were being actively developed in Estonia, drawing inspiration from Finland.

"Nocturnal songbirds are a rather special group of birds because their main singing activity takes place at night. If we are interested in bird populations, it is important to count them when they are easiest to hear," Elts explained on Vikerraadio.

Most birds sing actively in the early morning, but species classified as nocturnal songbirds are at their most vocal during the night. Estonia's best-known nocturnal songbirds include the corn crake, European nightjar and common nightingale. Many of them prefer habitats such as reed beds, thickets and shorelines along bodies of water.

According to Elts, most nocturnal songbird species are currently not doing well. The main reason is the loss of suitable habitat.

"We tend to tidy up every place: We clear away shrubs and drain wetlands. As a result, the habitats that nocturnal songbirds need disappear," he said.

The impact has been especially severe for species such as the river warbler and the grasshopper warbler whose populations have declined by more than 70 percent over the past 12 years. At the same time, some other species have remained stable, including the Eurasian reed warbler.

The corn crake, one of Estonia's best-known nocturnal songbirds, has also become less common. According to Elts, corn crakes were still frequently found in grain fields in the 1990s, but due to the intensification of agriculture, their main habitat has once again become grassland.

For the corn crake, it is important that mowing does not take place too early.

"We already see many mown areas now and naturally a corn crake cannot live in such a place," Elts said.

The nocturnal songbird census takes place in early summer, with participants typically traveling along predetermined routes between midnight and 3 a.m. All birds heard and, if possible, seen are recorded.

According to Elts, it is advisable to survey familiar terrain and inspect the route beforehand.

"Ending up in a thicket at 2 a.m. and finding it difficult to get out is not exactly the most pleasant experience," he said.

Elts recommends a route of around 10 kilometers, though the length depends on participants' abilities and the habitat being surveyed. Nighttime birdwatching also differs from daytime excursions in that fewer species sing at the same time, making their calls easier to learn.

At the same time, observers need to be able to distinguish the songs of different reed warblers and warblers such as the grasshopper warbler and river warbler, which can sound quite similar to beginners.

The main singing season for nocturnal songbirds lasts until Midsummer Day. After that, the birds become quieter, although individual singers can still be heard during the second half of summer.

Survey instructions and forms are available on the Estonian Ornithological Society's website. The society invites all nature enthusiasts to take part and contribute to monitoring Estonia's bird populations.

The data collected at night help scientists assess changes in nocturnal songbird populations and better understand how changes in landscapes and land use affect Estonia's birdlife.

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