With the onset of improving weather, if you keep your eyes to the skies you may start to see the first of our summer visitors arriving.
Swallows and house martins, which begin to arrive in April and May, will spend the summer feeding and breeding across the UK before flying back to Africa around September.
Their ability to use the eaves of houses as nest building sites has helped to increase their range and they are now found almost all over the UK, although particularly abundant in areas of Yorkshire and Lincolnshire.
As the birds spend much of their time on the wing, they can often be hard to differentiate.
However, there are a few key differences between the species which help with identification.
The swallow is the more colourful of the two species with a red throat, pale underside and a glossy dark blue back.
They also have long streaming tails which are often their most recognisable feature whilst in flight or resting on telephone lines.
Although the house martin also has a white underside and dark glossy back, a distinctive white rump and a shorter forked tail make it discernible from the swallow.
Although both species experience fluctuations in populations, widespread decreases have been seen in UK house martin populations since the 1970s.
The success of both species from year to year is highly dependent on weather conditions, especially during migration, with swallows arriving in worse condition and laying fewer eggs than in previous years.
Weather also impacts the birds on arrival, as if weather is too hot or cold, there is a reduction in flying insects, their main prey.
• For more information, visit www.rspb.org.uk