Exploring wildlife sounds through the seasons
Ecologists, conservation groups and nature enthusiasts have a long history of using sound to detect wildlife, from surveying bats in the field, to recording whales in the ocean. Many species use sound for communication and navigation, and their sounds are often distinct, so that we may identify their presence and behaviour in a given environment using the latest bioacoustic monitoring technology.
Bats, birds and other species exhibit a distinct seasonal behaviour that plays a crucial role in maintaining the balance of our ecosystems. Their activities, such as migration, breeding, and feeding patterns, change with the seasons, which is why each season’s soundscape has its own character and importance. We have found that surveying during a single season identifies as little as 50% of the total bird species that would be found in the land throughout the year.
As spring arrives in the UK, the chorus of birdsong reaches its peak, signalling the beginning of the breeding season. The dawn chorus, in particular, is an iconic feature of spring mornings, with a multitude of bird species joining in a symphony of songs. Birdsong is crucial for mate attraction and territory defence, with complex vocalizations conveying information about a bird’s quality and fitness.
In addition, the return of migratory birds to the UK in spring adds to the rich tapestry of birdsong, with many species arriving from long journeys from Africa and Southern Europe.
Bats will also start to emerge following their winter hibernation, reaching significant activity levels in May, which lasts through the summer.
The wren birdsong is a delightful and intricate melody often heard in woodlands, gardens, and hedgerows. As one of the smallest birds in Europe, the wren’s song is surprisingly loud and complex for its diminutive size. Its signature tune consists of a series of rapid trills, warbles, and chirps
The song thrush birdsong is a melodious and enchanting sound that fills the air in woodlands, parks, and gardens. Known for its distinctive, fluty voice, the song thrush weaves together a series of repetitive phrases and rich, varied notes, creating a delightful auditory tapestry. Its music often includes mimicked sounds of other birds and even non-avian sources, and is particularly notable during the early morning and late evening, when the song thrush establishes its territory and serenades potential mates.
The goldcrest birdsong is a delicate and high-pitched series of notes that can be heard in coniferous forests, mixed woodlands, and gardens. The goldcrest produces a rapid and continuous “zi-zi-zi” or “see-see-see” sound that has a slightly wavering quality, resembling the gentle tinkling of a tiny bell.
During the summer months in the UK, our landscapes are filled with the songs and calls of both resident and migratory bird species. Although the peak of birdsong occurs during spring, the summer season also offers a different auditory experience as birds engage in various activities, such as feeding and nesting.
Many birds are busy raising their young. Parents communicate with their chicks using a variety of calls to provide food, protection, and guidance. These brood-rearing calls are essential for the survival and development of the offspring. Birds learn birdsong through a combination of innate ability and social learning, especially during a key learning period when they are young.
Birds of prey can be commonly seen and heard, as they hunt more frequently to feed their growing offspring.
The willow warbler is a summer migrant to the UK, and its birdsong can be heard during warmer months. It has a captivating and melodious sound often heard in a variety of habitats, including woodlands, scrublands, and gardens. Characterized by its sweet, descending trill, the willow warbler’s song comprises a series of clear, plaintive notes.
The treecreeper bird call is a distinctive and unique sound often heard in forests and woodlands where these small, well-camouflaged birds reside. The call consists of a series of short, high-pitched, and evenly spaced notes that create a rapid, staccato-like rhythm. This sharp, repetitive pattern, sometimes described as a “tsee-tsee-tsee” sound, serves as a means of communication for the treecreeper, allowing it to establish territory, attract mates, and interact with other members of its species in the rich auditory environment of its habitat.
The coal tit bird song is a charming and easily recognizable sound, often heard in coniferous and mixed woodlands, parks, and gardens. The song consists of a series of clear, high-pitched notes, commonly arranged in a repetitive two- or three-syllable pattern, such as “see-saw-see” or “pee-poo-pee-poo.” The coal tit’s vocalizations have a lively and energetic quality, with a rhythmic cadence that distinguishes it from other tit species.
Summer at night
Echolocation calls from bats generally peak during the summer months. As temperatures rise during the summer months, insects become more abundant, providing an ample food source for bats. The increase in available prey encourages bats to forage more actively, which in turn leads to more frequent echolocation calls as they navigate and locate their prey.
Summer is also the mating season for many bat species, which means that bats are more active during this time as they search for potential mates. Echolocation calls may be more frequent and intense as bats communicate with one another and engage in courtship behaviours.
The brown long-eared bat (Plecotus auritus) echolocation call is a distinct acoustic signal used by this species to navigate and locate prey in their environment. These echolocation calls consist of frequency-modulated (FM) sweeps, which typically range from 25 kHz to 50 kHz, with a peak frequency around 35 kHz. The calls have a relatively low intensity and a long duration, usually lasting between 3 to 8 milliseconds. This combination of features results in a “whispering” echolocation strategy that enables the brown long-eared bat to efficiently hunt for insects near vegetation and foliage, while minimizing the risk of detection by both prey and predators.
Bat Echolocation calls are not audible to us, but by recording at ultrasonic frequencies, we can then reduce frequency and slow the recording down to listen.
During autumn in the UK, the landscape of bird calls undergoes a shift as the breeding season comes to an end, and resident birds adjust to the changing environment. Migratory birds who have resided in the UK over the summer will prepare for their return journeys, and winter residents will start to arrive in late autumn.
With the breeding season over, the intensity and frequency of birdsong decline significantly. However, other bird calls, which are equally species-specific as birdsong, become increasingly prevalent.
As birds form flocks for foraging, roosting, or migrating, they rely on contact calls to communicate with each other and maintain group cohesion. Species like Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus) can often be heard making short, sharp calls as they gather in large flocks. As the leaves fall and trees become more bare, birds become more vigilant, and alarm calls may become more frequent. These calls alert other birds to potential dangers or predators nearby, such as cats or birds of prey.
Bats will continue to be active in early autumn, when it is still a good time to monitor their activity, before starting their hibernation period in October/November.
The kestrel bird call is a distinctive vocalization that can be heard in a variety of habitats, frequently grasslands and open fields, where they are likely to reside. The call is characterized by a series of high-pitched, shrill, and repetitive “klee-klee-klee” or “kee-kee-kee” notes. The sharp, piercing quality of the kestrel bird call makes it a notable and recognizable sound. The kestrel’s vocalizations serve multiple purposes, such as communication between mates, signaling territorial boundaries, or expressing alarm in the presence of potential threats.
The great tit call, known for its versatility and rich vocal repertoire, sometimes incorporates clicks into its vocalizations. This distinct call, characterized by a series of short, sharp clicks or “chit-chit-chit” sounds, is often used to communicate, or convey a sense of urgency or alarm in response to potential threats or disturbances. The clicking call is typically produced in rapid succession, creating a staccato-like rhythm. Various alarm calls are likely to be heard at this time of year, when birds are on greater alert.
The chaffinch call is a distinctive and melodic vocalization that can be heard in various habitats, as it is one of the most widespread and abundant birds in Britain and Ireland. The call is characterized by a series of clear, short notes, often described as a “pink-pink” or “hweet” sound, which serves as a contact or alarm call. In addition to these calls, the chaffinch is also known for its captivating song, which consists of a combination of trills, warbles, and descending notes, culminating in a distinctive, emphatic flourish.
During winter in the UK, the soundscape of bird calls again transforms as a result of the colder temperatures, reduced daylight hours, and changes in bird behaviour. Some birds will continue to be highly active during this season. The Robin (Erithacus rubecula), will continue to defend their territories, use their melodious song and calls to mark their territory and warn off rivals. You can often hear its song in the evening, as well as the morning.
The arrival of winter visitors from colder regions brings a variety of new bird calls to the UK soundscape. Some examples include the high-pitched calls of the Redwing (Turdus iliacus) and the trilling calls of the Waxwing (Bombycilla garrulus), which can be heard as they forage for food in gardens and hedgerows.
Towards dusk, birds like Starlings (Sturnus vulgaris) and Rooks (Corvus frugilegus) can be heard producing a cacophony of calls as they gather in large roosts to stay warm and safe during the cold winter nights.
The robin’s birdsong during winter in the UK is a distinctive and heartwarming sound that can be heard during the morning and later afternoon on most winter days. As one of the few birds that continue to sing throughout the winter months, it is sometimes the only song that can be heard. The song itself is characterized by a series of clear, melodic phrases, featuring rich, warbling notes interspersed with occasional pauses. The winter robin birdsong tends to be softer and more reflective compared to its vibrant spring counterpart, but it remains a beautiful and soothing reminder of nature’s resilience and adaptability in the face of seasonal challenges.
The grey heron call is a distinctive and easily identifiable vocalization, often heard in wetlands, marshes, and riversides where these large wading birds reside. The call is characterized by a deep, guttural, and harsh “fraaank” or “kraaak” sound, which may be repeated in a series or delivered as a single note. These vocalizations serve various communicative purposes, such as signaling alarm, establishing territory, or maintaining contact among individuals within a colony.
Redwing migrate to the UK over winter, with the first travellers arriving in October. The redwing call can be heard in woodlands, hedgerows, and fields where these migratory thrushes reside, especially during the winter months. The call is characterized by a series of high-pitched, thin, and slightly descending “seep” or “tseep” notes, which are often delivered in rapid succession. These calls serve as contact and alarm signals among individuals, facilitating communication and coordination within flocks as they forage or travel.
Winter at night
You may expect night time during the colder months to be a very quiet period, but Owls can often be heard during this time, as the longer nights mean these nocturnal birds have more time to engage in courtship and nesting activities. British owls generally start nesting during late winter and early spring, but the timing varies depending on the species.
Owls are active throughout the year, and are busy hunting to meet their energy needs and, during the summer months, to provide food for their growing offspring.
The tawny owl, a widespread nocturnal bird found in woodlands has different calls for male and female. Its calls serve various communicative functions and are easily recognizable in the night:
- Hoot: The male tawny owl’s most familiar call is a series of deep, resonant hoots, often transcribed as “hoo-hoo” or “hoo-hoo-hooo.” This call serves to establish territory and attract potential mates.
- Kewick: The female tawny owl produces a shorter, sharp, and high-pitched call, typically written as “ke-wick” or “ke-wik.” This call is often used as a contact call or a response to the male’s hoot.
- Duet: Male and female tawny owls occasionally engage in a duet, where the female’s “kewick” call is followed by the male’s hooting, creating a distinctive back-and-forth vocalization.
The Barn Owl (Tyto alba) is known for its relatively silent flight and ghostly appearance, but it does produce a variety of vocalizations, particularly during the breeding season. The most common and distinctive call of the Barn Owl is a loud, raspy screech or hiss-like sound, which can be described as eerie and unsettling to those who are unfamiliar with it.
This screeching call is often emitted by adult Barn Owls when they are communicating with their mates or defending their territory from intruders. The call can be heard at dusk or during the night when Barn Owls are most active. In addition to the screech, Barn Owls produce other vocalizations, such as soft chitters, clicks, and snores, which are used in various social contexts, including mate attraction and communication between parents and offspring.
A multi-season approach to monitoring
If we only survey one time of year, we only register a fraction of the nature that inhabits and travels through our landscapes. Many of the threatened species in the UK, and those of conservation concern, are migratory and spend only part of the year here. We’ve found that limiting your surveying to a single season identifies as little as 50% of the total bird species that would be found in the land throughout the year, showing the importance of a multi-season survey approach.
Multi-season monitoring plans are crucial for understanding wildlife populations, behaviour, and ecology across different seasons. Bioacoustics unlocks our ability to deliver long-term monitoring at scale, delivering essential data to inform conservation and habitat management strategies, ensuring the long-term health and stability of our nature.
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