Biebrza Wetlands: Birdwatching in Poland's Largest National Park

Biebrza National Park protects 59,223 hectares of river valley, peat bogs, and floodplain forest along the Biebrza River in northeastern Poland. It is the largest national park in the country by area and holds one of the most significant wetland bird assemblages in central Europe. The park sits on the East Atlantic Flyway — the migratory corridor connecting Arctic breeding grounds to West African wintering areas — and functions as a critical stopover and breeding ground for waterbirds and marsh passerines.

The spring period between late March and mid-May is the principal observation window. At this time the floodplain is at its most expansive, migratory species are arriving, and resident species are in full breeding display. Most of the ornithological documentation on Biebrza was produced during this window.

The Spring Flood Window

The Biebrza River floods its lower valley almost every year between March and May. The extent varies — in some years the water reaches only the lowest meadows; in exceptional years (2010, 2017) it covers areas visible from elevated viewpoints as a continuous sheet of water several kilometres across. For bird observation, the flood is highly productive: it concentrates wading birds on elevated ground, fills temporary pools that attract ducks and geese, and triggers lekking (communal mating display) in several ground-nesting species.

The aquatic warbler (Acrocephalus paludicola), one of Europe's most threatened passerines, breeds here. Biebrza holds the largest known breeding population outside of Belarus — approximately 10,000 singing males in peak years, according to data from the Polish Society for the Protection of Birds (OTOP). Hearing and locating the species requires presence in the southern basin (Dolny Basen) between late April and early June.

Key Species by Season

Spring (late March – May)

• Greater white-fronted goose and bean goose — thousands present during March flood peak
• Ruff — lekking on elevated meadow edges, late April
• Black-tailed godwit — floodplain meadows, April
• White stork — returns from late March; visible at virtually every farm edge
• Common crane — northbound migration March–April; some pairs breed in the park
• Marsh harrier — widespread across the entire valley from April
• Aquatic warbler — southern basin, from late April
• Little crake and spotted crake — reed edges, May; heard more often than seen

Summer (June – August)

• Great bittern — booming from reed beds at dawn, June
• Black stork — breeds in the forested sections of the northern basin
• Corncrake — rasping call audible at night across hay meadows throughout July
• White-tailed eagle — present year-round; multiple pairs breed

Autumn (September – October)

• Whooper swan — southbound flocks through October and November
• Greylag goose — large staging flocks in the lower basin
• Golden eagle — occasional, often following the river corridor

The Red Trail (Czerwony Szlak): Main Observation Route

The Red Trail runs 67 km through the park from Sztabin in the south to Osowiec-Twierdza in the north, following the western edge of the Biebrza valley. It was designed specifically to provide access to the most ecologically productive sections of the floodplain without crossing the bog surface, which is unstable and ecologically sensitive.

Key observation points along the Red Trail:

• Osowiec-Twierdza observation tower: 12-metre wooden tower overlooking the flood meadows of the Middle Basin; most productive in early morning between mid-April and mid-May
• Goniadz viewpoint: elevated ground overlooking the river bend; reliable for crane and goose staging in March–April
• Gugny area: access to the bog surface via boardwalk sections (check current trail status at the park office); aquatic warbler habitat
• Dolistowo Stare road: gravel road alongside the lower basin; driveable slowly at dawn for crane, godwit, and ruff on flooded meadows

The full Red Trail requires 3–4 days to walk end-to-end with overnight stops at designated camping sites. Most ornithologists cover sections independently by car, stopping at observation points. Rubber boots are essential from March to June as the trail crosses wet meadows that remain flooded after the main recession.

Practical Access

The park headquarters and main visitor centre are located in Osowiec-Twierdza, accessible by regional bus from Białystok and Łomża. The fort complex at Osowiec (19th-century Russian military fortifications, open to the public) provides the main visitor infrastructure including maps, guided tour booking, and current water level data.

No entry fee applies to the buffer zone or most of the trail network. The park does charge for designated camping sites (approximately 15 PLN per person per night) and guided bog excursions. Independent walking on marked trails does not require prior registration.

The nearest accommodation options are in Osowiec-Twierdza, Goniadz, and Rajgród. The area has limited tourist infrastructure; guesthouses and agrotourism farms are the primary options. Booking in advance is necessary for the April–May peak.

Low-Impact Observation Rules

• Walking on unmarked bog surfaces causes permanent damage to the peat structure and is prohibited throughout the park
• Photography from a hide or at a distance of more than 100 m from active nests is the accepted standard — approaching displaying or nesting birds causes measurable reproductive failure
• Playback of bird calls to attract species is discouraged by the park and by OTOP guidance; it is particularly harmful during the breeding season for crakes and warblers
• Dogs are prohibited from the nature reserve sections of the park
• Vehicle access on unpaved roads within the park requires a permit from the park directorate