Even birders who are fantastic at birding by ear can be fooled by bird mimics, but why would one bird impersonate another and how can you learn to tell the difference? Understanding what birds are mimics, what unusual sounds they use and why they have such an unusual repertoire of songs and sounds can help birders puzzle out these unexpected noises.
What Birds Mimic
A wide variety of birds mimic different songs and sounds, and mimicking is widespread in many types of birds, including the corvids, parrots, bowerbirds and mynas.
Birds in the Mimidae family are accomplished mimics, and many species from a wide range of scientific families have at least some mimicked sequences in their most common songs and calls. Species known for their mimicking vocalizations include:
- African gray parrot
- American crow
- Blue jay
- Brown thrasher
- Crested oropendola
- Eurasian jay
- European starling
- Gray catbird
- Lawrence's thrush
- Marsh warbler
- Northern mockingbird
- Steller's jay
- Superb lyrebird
Individual birds can have widely varied mimicking repertoires, with as many as 200-2,000 unique sounds included in their vocalizations. In general, the older and more experienced the bird is, the more sounds it has learned to mimic and the more complex its songs and calls will be. Younger birds will first mimic the sounds their parents make, then eventually expand their own repertoire with other sounds from their environment.
With the complicated syrinx that creates a bird's voice, they have a wide range of tones, pitches and sounds they can use while mimicking.
While the alarm or threat calls of other bird species are some of the most mimicked tones, other unexpected sounds birds will reproduce include:
- Cell phone ring tones
- Car alarms or other vehicle alarms, such as sirens
- Music, especially repeated tones such as from a store or carnival
- Construction equipment noises
- Cats, dogs or other predators
- Human speech
Even birds of the same species may not mimic similar sounds. The exact sounds included in any bird's vocalizations depend on what sounds it is exposed to in its environment. Therefore, urban birds are often better mimics of non-natural sounds, while birds in tropical regions with more diverse avifauna are more likely to mimic a wider variety of other bird species.
Why Birds Impersonate Other Birds
There are many reasons why birds take advantage of mimicry, and often the same bird will use mimicked sounds for different reasons. While more study is needed to see just how a bird's use of different sounds affects its behavior and survival, the most common reasons for a bird to mimic include:
- Impressing a Mate: Songs are a large part of bird courtship behavior, and a more varied song that includes different mimicked tones can help attract a better mate. Because mimicked tones are learned, a bird with more variety in its song is demonstrating its intelligence, ability to survive and other characteristics that a mate would find desirable.
- Nest Protection: Some birds mimic predator songs or other bird threat calls, such as a hawk or owl screech, while nesting to discourage other birds from approaching the nest. These songs can scare other birds away if they believe the territory is dangerous, which will keep it safer for the brooding bird and its hatchlings.
- Safeguarding Food: Using a hawk or owl call, or the sound of a cat, dog or other predator, is an effective way for a bird mimic to claim a food source. When it utters such a call, birds monopolizing feeders or favored bushes, trees or other feeding spots may scatter, letting the mimic take advantage of a less crowded food source.
- Defending Territory: Songs are crucial for many birds to claim territory, and adding mimicked tones into the song can demonstrate the resident bird's strength. Extra sounds may also trick other interested birds into believing that there are far more birds in the region than there actually are. The newcomers may then simply move along rather than challenge the resident mimic bird.
- Social Acceptance: Baby birds learn many songs from their families and other birds of their species, and if mimicked sounds are included, then young birds will learn them as part of their initial repertoire. This helps birds fit in with their flocks, which will also help them eventually defend their own territories and attract mates. Many pet birds that learn to mimic speech are doing so for social acceptance, as they consider humans as part of their flock.
- Accidental Learning: In some cases, birds accidentally mimic unusual sounds just because of proximity. This is often the case with urban birds mimicking construction equipment, car alarms and other mechanical sounds. It is unlikely that many of those sounds will be appealing to other birds, but because they are common, ambient sounds in the birds' habitat, they become included in the repertoire all the same.
Identifying Bird Mimics
When a bird doesn't sound like itself, it can be difficult for birders to listen to the bird and accurately identify the species. With a careful ear, however, there are tricks that can help identify even the most accomplished mimics.
- Use whatever sounds the bird is making – no matter how unusual they are – to find its location so it can be identified visually with field marks, size, shape and other standard characteristics.
- Listen carefully for a change in the bird's song; a songbird that rapidly switches to different tones or radically changes its vocalizations is likely a mimic rather than whatever bird it may sound like.
- Consider habitat for proper identification. No matter how convincing the sound, it is unlikely that a hawk or owl would be calling during the day in a thick forest, but a jay may be mimicking their voices.
- Identify the song's pattern, including the cadence, how many repetitions each section of the song has and how its tempo changes to help identify the mimicking bird.
Identifying a bird mimic is always challenging, but hearing these birds can give every birder greater appreciation for avian acoustics.