A quasi live reporting of bat movements along the Baltic Sea coast.

The hidden spectacle of thousands of bats migrating, reported from Pape Station at the Baltic Sea coast in Latvia. How many bats passed last night? What was the weather like, and how did the bats respond? Our monitoring provides the answers to these questions, offering invaluable insights into the mysterious behaviour of these nocturnal mammal migrants.

By sharing our observations, we aim to raise people's awareness for migratory bats and inform bat workers across Europe about the current bat movements at our site. Detailed data are subject to specific research programmes, feel free to get in touch for further questions.

BatCast24 is supported by volunteers and collaboration partners.

Recent Observations

2024/09/09-10 #36 The night will be challenging due to strong winds and northeasterly orientation. The trap has been taken down.

Midnight update: Bat activity was low, as expected, with very few bats recorded in the 1st half of the night. Three Pnat bats were observed over a 15-minute period.

4 o’clock update: The acoustic monitoring showed no change in activity. However, surprisingly, towards the morning hours bat activity increasing to 5 bats per 3 minutes.

2024/09/08-09 #35  The wind is forecasted to come from the southeast, yet with moderate intensity of 6 m/s. This may lead to fewer bats flying in the dunes but more passing by the trap on the sea side instead.
Midnight update: The evening started off quietly, similar to the previous nights. Only 2 bats passing per 3 minuteswereregisteredduring the first acoustic count. Now, we observed 6-7 bats per 3 minutes. This uptick in bat activity gets reflected in the trap, with more and more bats entering.

2024/09/07-08 #34 The warm period continues to affect us with an expected drop to 19°C. Southeasterly winds with up to 4 m/s are forecasted, likely to lead to a strong migration at our site.
Midnight update: The evening started slowly, with only 3 bats observed in the first half-hour. As a result, the trapping was paused. Theacoustic monitoring revealed a bat activity of 3 bats passing per 3minutes.
4 o’clock update: We noted an increase with 5-6 bats passing per 3minutes, which prompted us to resume trapping. By ~03:00, the activity dropped back down to 3 bats per 3 minutes, although some still enteredthe trap. Despite the relatively calm winds, many bats were observed flying past the trap and over the beach. In total, 162 bats from 5 species were caught: Pnat, Ppyg, Vmur, Plaur and Mdau.

2024/09/06-07 #33 It remains warm with a drop to 18°C. Easterly winds with up to4m/s are forecasted but a shift to southeast is expected for the 2nd half of the night. We might see a strong migration.
Midnight update: The night started off moderately well, with a few dozen bats flying into the trap. The first acoustic counts revealedapprox. 8-9 bats passing per 3 minutes. However, the activity in the trap began to pick up more noticeably after the second count.

2024/09/05-06 #32 Like yesterday, it will remain warm, with temperatures expected to drop to 18°C. Easterly winds with gentle breezes of up to 4 m/s were forecasted, but after sunset, there was no wind at our site. How these conditions will affect bat migration tonight remains unclear.

2024/09/04-05 #31 The weather forecasts again indicate easterly or southeasterly winds with gentle breezes of up to 5 m/s. The night will be quite warm, with temperatures expected to drop to 19°C. We could see a few hundred bats again.

Midnight update: There also was almost no wind in the dunes. The usual peak of "first flyers" after sunset could not be observed; no bats could be caught. At least the acoustic monitoring revealed that 4 bats passed per 3 minutes. But also this seemed to fluctuate and sometimes no bats flew for many minutes.

7 o'clock update: Conditions changed for the better in the 2nd half of the night.  The wind got slightly stronger, and especially many parti-coloured bats (Vmur) started flying into the trap; these could also be recognised in the acoustic monitoring. The flyby-rate overall increased to 7-8 bats per 3 minutes. In total, we caught nearly 2x as many bats as yesterday with 389 animals from 4 species: Pnat, Ppyg, Vmur  and an additional Plaur.

2024/09/03-04 #30 Weather conditions are expected to be relatively mild with temperatures reaching 17°C. Regional weather forecasts indicate the possibility of easterly or southeasterly winds of 3-4 m/s. While it is uncertain whether this gentle breeze will result in a significant influx of bats, it is a possibility.

Midnight update: There were only a few bats after sunset, and now it is silent. During the first  acoustic monitoring session, only 3 bats were detected per 3 minutes despite near-perfect wind direction, strength, and temperature.

7 o’clock update: By the second detector count, bats were visible over the beach, but too close to the sea to enter the trap. At the third count, their flight paths shifted further inland, allowing the detectors to pick up slightly more activity - 4 bats per 3 minutes and the bats  began entering the trap again. In total, 206 bats from 4 species were caught: Pnat, Ppyg, Vmur and a single Mdau.

2024/09/02-03 #29 Monday. The night will be dominated by a light breeze from the northeast, with gusts up to 5 m/s. Temperatures will drop to at least 12°C, so we do not expect a strong influx of bats.

Midnight update: The wind is unfavourable, causing bats to fly high over the dunes in small numbers. As a result, the detectors are not registering many bats, nor are they entering the trap. 

4 o'clock update: The number of bats recorded acoustically has significantly increased; however, the bats appear to prefer flying further inland. In the last hour, some bats have started entering the trap again. A total of 86 bats from 3 species - Pnat, Ppyg, Vmur - have been caught. Then, catching was stopped despite the continued bat activity, as the cold temperatures were causing the caught individuals to take too long to take off again. This decision was made in the interest of animal welfare.

2024/09/01-02 #28 The temperatures will stay >15°C, winds will blow from the northeast in the 1st half of the night but are forecasted to shift southeast coming with a light breeze. We might expect a strong influx of bats, esp. in the 2nd half of the night.

6 o'clock update: The number of bats flying into the trap indeed increased in the 2nd half of the night. In total, 530 bats have been caught from 4 species: Pnat (501 individuals), Ppyg, Vmur and Nnoc.

2024/08/31-01 #27 The trap is up again. Wind may be more optimal for catching in the 2nd half of the night blowing from the southeast, however, with only 1-3 m/s. Temperature down to 12°C according to the forecasts.

Midnight update: There are 1-4 bats per 5 minutes flying along the dunes. The movements resemble migration flights in their straightness; however, the bats are moving bidirectionally, with equal numbers flying northwards and southwards.

6 o'clock update: The number of bats flying into the trap was small, indeed. In total, 23 bats have been caught from 2 species: Pnat and Ppyg.

2024/08/30-31 #26 A storm is approaching from southeast which we expect to hit the station around 11PM.

Midnight update: In total, 75 bats from 2 species were caught: Pnat  and Ppyg.

Below, in the morning, the trap is visible, lowered for safety reasons.

2024/08/29-30 #25 The temperatures remain relatively high, above 17°C, but there is no cloud cover. Winds are blowing from the southeast, so we can expect a good migration again.
Midnight update: A massive migration is underway, with an intensity never before observed. This may be due to the improved technologies we have available this year. The trap is full of bats, while many others are passing by on the seaside and over the trap due to the headwind. Bats are easily visible against the starlit sky. The detectors are constantly active, registering one flyby every 1 to 2 seconds. Anyway, the trap is full with bats while many are passing by on the sea side and over the trap. Bats are easily visible against the starlit sky. The detectors are no longer quiet but clatter all the time; one flyby every 1 to 2 seconds.
6 o’clock update: The highest number of bat passings, measured with a bat logger in the dune forest, occurred after midnight and exceeds 300 calls. This is just a 'spatial snapshot' captured by the microphones, which are, of course, limited in their detection range. In total, 2175 bats from 5 species were caught: Pnat, Ppyg, Vmur, Nnoc and Enil.

Below, one bat logger and the bat call detection summary for the 2nd half of the night.

2024/08/28-29 #24  The wind has changed, now blowing with 1 m/s from the southeast. It is unclear wether this will be enough for a strong influx of bats.

Midnight update: Bats are constantly entering the trap. A massive migration just started*.

5 o’clock update: This night's catch represents a record for our station. In total of 2,605 bats from 6 species have been caught, with over ten times more Pnat (2300+) than Ppyg. Additionally Vmur, Mdau, Mnatt, and Bbar were caught.

*Note: Despite the large number of bats caught in the trap, none of the animals were injured, thanks to the excellent work of our team. Special recognition goes to Agate D. Ozoliņa, who not only caught the most bats but also proved to be the most enduring bat catcher this season so far.

2024/08/27-28 #23  The weather will not be ideal for catching bats, however, the trap is up and ready.

5 o’clock update: In total, 133 bats from 2 species have been caught: Pnat and Ppyg.

2024/08/26-27 #22 Monday. The trap is up again as the winds will be more optimal for catching blowing from the southeast, however, with only 1-3 m/s. The temperatures are dropping to below 10°C. We can hope for some bats migrating along the coastline.

1 o’clock update: A little more than 500 bats have been caught. More than 450 Nathusius’ bats Pipistrellus nathusii (Pnat) predominate the count. With a bit of luck, we will have >100 Soprano pipistrelles P. pygmaeus (Ppyg) in the morning. Natterer’s, Northern and Barbastelle bats are among those bats caught so far. While ground fog is rising behind the dunes, the trap remains unaffected from it.

4 o’clock update: In total, 889 bats from 7 species have been caught: Pnat, Ppyg, Brandt’s bat Myotis brandtii, Whiskered bat M. mystacinus, Natterer’s bat M. natt., barbastelle Barbastella barbastellus, Northern bat Eptesicus nilssonii. As expected, the Nathusius’ pipistrelles dominated in numbers.

2024/08/25-26 #21 The trap is down again as the winds blow unfavourably from the sea.

5 o’clock update: Activities judged by detector counts were very low throughout the night.

Late morning update: If bats flew further inland, one might expect some flew past wind turbines that operate in several locations along the A11, quasi one to ten kilometres parallel to the coastline.

Below, another find of an injured bat under a wind turbine.

2024/08/24-25 #20 The trap is up again as the conditions for catching bats this night appear ideal, with winds of 3-5 m/s from the southeast.

11 PM update: Around 184 bats, predominantly Nathusius’ bats (Pipistrellus nathusii), have been caught. This is not the mass migration we expected, so far.

Midnight: The number of bats has risen significantly, with over 500 individuals caught. Soprano pipistrelles (P. pygmaeus) are still flying in, and now Parti-coloured bats (Vespertilio murinus) are also in the mix.

6 o’clock update: A total of 2372 bats from 7 species have been caught, indicating a mass migration. Nathusius’ pipistrelles Pnat lead the count with 2,017 individuals, followed by Ppyg and Vmur. Additionally, we caught one each of the common noctule Nyctalus noctula, Eptesicus nilssonii, Myotis daubentonii, and M. nattereri.

2024/08/23-24 #19 Storm, strong wind >9 m/s from the sea and the south, with strong gusts of wind. The trap is down.

3 o‘clock update: Some bats were migrating despite the winds, but further inland; in the first acoustic counts there were approx. 2 per 10 min, in the second count after midnight numbers rose to 40 to 50 per 10 min.

Afternoon update: If bats flew further inland, one might expect some flying past wind turbines that are one to ten kilometres parallel to the coastline.

Below, a fresh carcass of a bat found below a wind turbine at noon.

2024/08/22-23 #18 Storm, strong wind >7 m/s from the sea. Trap was up only for 20 minutes and a single Nathusius' bat has been caught. Against the bright moon light, bats were observed to fly next to the trap in the wind shadow of the dune.

2 o‘clock update: Bats are flying behind the coastal forest, i.e., east of the pine trees of the station. Acoustic counts recorded through a logger launched into the sky to 30 m height using a kite, show an activity peak just before midnight; Pnat, Ppyg., Vmur and other Nyctaloid bats. A single Pnat was caught.

2024/08/21-22 #17 Storm. No bats were observed; the trap was not set up, and no bats were acoustically recorded during the nightly counts.

2024/08/20-21 #16 The wind will blow from the east again, the windspeed reaches 3 m/s. This constellation could indicate that we will see bidirectional orientation of freely flying bats.

Midnight update: One bat every 2 minutes were acoustically detected. After two ours ~200 bats have been caught, with the majority being Nathusius’ bats (Pnat) and a few Soprano pipistrelles (Ppyg).

5 o‘clock update: In total, 1217 bats from 4 species were caught. Two barbastelles (Barbastella barbastellus) were a rare highlight in the dunes, along with Pnat, Ppyg and Vmur.

2024/08/19-20 #15 Monday. The wind will shift to the southeast, increasing our chances of seeing many bats; the trap is pulled up again. However, the wind strength may be slightly too weak for a mass migration (>1,000 bats) near ground level.

Midnight update: After a short but intense influx of bats at dusk, one bat per minute is now flying into the trap. A total of 317 bats have been caught so far, with the majority being Nathusius’ bats (Pnat). Soprano pipistrelles (Ppyg) are now lower in numbers, with fewer than 20 individuals caught.

4 o‘clock update: Bats are still flying. Two-hundred bats were registered acoustically in just the last 45 minutes.

5 o‘clock update: Two Northern bats, a Brandt's bat, and a common noctule have been added to the night's catch of mostly Pnat and Ppyg. In total, 762 bats from 5 species have been caught.

Below, as the evening approaches, the trap nets are being pulled up again.

2024/08/18-19 #14 A storm coming from the sea and towards Pape has been forecasted. We are taking down the trap soon after sunset. However, 19 Nathusius' bats could be caught in less then 10 minutes.

Midnight update: The storm remains a threat. Masses of bats appear to migrate but the integrity of the trap and safety remains our priority.

Morning update: Bats were swarming over the ringing house before sunrise. The automatic acoustic recordings revealed that we had had a mass migration event.

Below, the acoustic recordings of the last two weeks illustrate this night's migration has been the largest bat movement this season so far.

2024/08/17-18 #13 The wind will blow with low intensity, directions might not have any influence. Temperatures will drop slightly.

Midnight update: With one bat per 5 minutes in the mean, the numbers are not promising for the remainder of the night, indeed with >30 min of no bat having been sighted, a break is due.

4 o‘clock update: In total, 21 bats from two species were caught: Pnat, Ppyg.

Below, the pipistrelle caught just before midnight has been the last animal this night. 

2024/08/16-17 #12 The wind will blow with an ideal orientation from SW in the first part of the night but is assumed to change later. Wind strength may be a little too high for mass migration.

Midnight update: With one bat per minute in the mean, the numbers are significantly smaller than in the night before; 143 bats have been caught from 4 species: Pnat, Ppyg, Enil and Vmur. Nathusius‘ pipistrelles are now more in numbers than soprano pipistrelles.

4 o‘clock update: A common noctule (Nnoc) and a Brandt’s bat add to this night’s list of species. In total, 323 bats were caught. The trap is now taken down as a storm is about to hit us.

Below, the decline in numbers in the 2nd half of the night is illustrated based on numbers of acoustic recordings acquired 100 m north of the trap. 

2024/08/15-16 #11 The wind will blow with an ideal orientation and strength for bat catching.

Midnight update: More than 1,000 bats are caught already. In total from 5 species: Pnat, Ppyg,  Nnoc and Vmur. Pipistrelles comprise the majority of the catches, we celebrate the catch of a Lesser noctule Nyctalus leisleri.

Morning update: After 2 AM the influx of bats slowly ceased. In total 1,297 bats were caught. 

2024/08/14-15 #10 Cloud cover is about to reach at least 50%, and the wind strength will remain low, with an ideal orientation for bat catching.

Morning update: We breached the four-digit mark, with 1,133 bats caught in total from 5 species: Pipistrellus nathusii (Pnat), Pipistrellus pygmaeus (Ppyg), Nyctalus noctula (Nnoc), and Vespertilio murinus (Vmur). Pipistrelles comprise the majority of the catches, with P. pygmaeus still outnumbering the other species.

2024/08/13-14 #9 The weather is about to change. Cloud cover will increase over night, temperature is expected to drop by approx. 5°C, the wind directions is supposed to change to ideal-for-bats NW orientation. However, the wind strength is assumed to remain low. Not clear whether bat migration will intensify  compared to last night. Our trap will be set up.

Morning update: The first bat of the year, a Nathusius' pipistrelle, was caught 45 minutes after sunset, soon followed by an influx of Soprano pipistrelles. In the second half of the night, migration intensified. In total, 438 bats from 8 species were caught: Pipistrellus nathusii (Pnat), Pipistrellus pygmaeus (Ppyg), Nyctalus noctula (Nnoc), Eptesicus serotinus (Eser), Eptesicus nilssonii (Enil), Vespertilio murinus (Vmur), Plecotus auritus (Plaur), and Myotis daubentonii (Mdau). As expected, the pipistrelles dominated in numbers. 

2024/08/12-13 #8 Monday. Clear sky with the occasional cloud. Half-moon bright after dusk, setting before midmight. Aurora visible over central Latvia in first half of the night. The weather forcast is wrong before and during the night about the intensity of the wind; wind remains well below 7 m/s. Sea with moderate waves. Quite warm still, 17°C in th mean for the night. Trap is down for technical reasons. Acoustic and visual counts confirm southward flight directions of bats but the number of individuals is low , i.e. one flyby every 5-10 min. Soprano pipistrelles P. pygmaeus are dominating the records by far. Others are Nathusius' bats (P. nathusii) and Nyctaloid species.

2024/08/11-12 #7 Clear sky with the occasional cloud. Sea with moderate waves, fresh breeze from the west (9+ m/s). Quite warm, 19°C, also after mignight. Our trap remains grounded to protect the nets. Acoustic and visual counts confirm southward flight directions of bats but the number of individuals is very low, i.e. one flyby per 15 mins. Nyctaloid bats, Pipistrellus nathusii and P. pygmaeus recorded. Local northern bats Eptesicus nilssonii are present constantly, foraging behind the dune's forest.

2024/08/10-11 #6 Storm. No bats.

2024/08/09-10 #5 Storm. No bats.

2024/08/08-09 #4 Winds zero to low with max. 3 m/s, light rain between 0-1 AM, bats quite active but it appears that all this was local movements, i.e. foraging related.

2024/08/07-08 #3 No wind. Very few bats were flying; majority northwards. Not sure, that it could be called migratory movements what we have seen that night.

2024/08/06-07 #2 Low northerly winds, resulted in low numbers of bats flying. Yet, the few bats that were passing appeared to be migrating in most cases, i.e. they flew straight along the dunes. However, most bats were oriented northwards (!) 

2024/08/05-06 #1 Monday. Greetings from Pape, where bats are happily migrating. One hour observing visually: mid to high flight heights, bats orienting southwards. One bat every three minutes. Tailwind of 4 to 5 m/s, with no need perhaps to fly low, in the wind shadow of the tree canopies. However, a small number of bats flying northwards, very low against the wind.