Sound recording in the field is an essential tool of many people studying wildlife. It can be used to gauge what bird species are in an area without having to actually see the elusive individuals, or to discover what animals are active after dark. Researchers may wish to make detailed recordings of a particular species in an attempt to understand, for example, social interactions or territorial behaviour.

There is a wide range of cheap sound recording equipment available on the market these days but, although fine for recording voice dictation or music, they are often not suitable for recording wildlife in the field. To record clear and meaningful data, good quality, specialist equipment should be used. The basic items needed before heading out into the field are a microphone with parabola or a direction gun microphone, a portable recorder (plus any battery and memory cards for the recorder) and good audio connecting leads. You may also need a tripod or headphones.

Recording in mono is more often used for studying an individual animal. Stereo tends only to be used when making general recordings of activity in an area or recording a group of animals. Some animals use ultrasound and therefore require specialist equipment to convert the sounds to be able to be picked up by a normal recorder. For example, bat echolocation calls can be converted to audible sound by a bat detector, which can then be connected to your recorder.

The main problem with recording wildlife in the field is background noise such as traffic or wind. There are a number of microphone options to overcome this:

A parabolic reflector (or parabola) is basically a dish which focuses distant sounds down into the microphone. The larger the dish, the higher the amplification - but it can be difficult to carry huge parabolas into the field, 50cm diameter is a popular size. Small parabolas may be unsuitable for recording low frequency sounds (such as from large animals like lions) as the wavelength of sound can be longer than the dish diameter. In general a 50cm parabolic reflector is fine for anything above 600Hz.

Dynamic microphones with cardioid response can be used with parabolas and have the advantage in the field that they are relatively robust and do not require an additional power source. Condenser-type microphones are a more expensive option and require additional power but will give higher quality recordings. Some parabolas come with a built-in microphone.

Gun microphones (also known as super-cardioid or ultra-directional) can be used instead of parabolic reflectors. They are far less bulky to carry out into remote locations but can suffer from handling noise so using with a pistol grip and shock mount is highly recommended. Gun microphones are usually of the condenser type and require a power source. Short gun microphones are ideal for subjects that you can approach closely such as amphibians and insects. The long gun type should be used for more elusive subjects such as mammals and birds.

A windshield for your microphone is essential in most outdoor locations. The cheapest option is a foam sleeve which slides on over the microphone, suitable for low wind areas. The next is the "shaggy" sleeve type which tends to cut out more wind noise but is usually more expensive. The most effective is a cage windshield but these are costly pieces of equipment. Wind covers are also available for parabolas.

When choosing a recorder for fieldwork, you should look for lightweight yet robust models with easy-to-use controls. Backlit display/buttons are always useful when recording in low light or dark conditions. Automatic gain controls and noise reduction functions should not be used when recording wildlife sounds. Units with built-in speakers can be helpful to quickly check recordings in the field, alternatively carry a set of headphones.

Cassette recorders were once the most popular method for beginners and people on a low budget. The tape running speed of a unit can vary and should be regularly calibrated or use a reference tone at the start of each set of recordings made. Cassette recorders have now given way to other formats such as minidisc, solid state and MP3 recorders due to their more compact size, recording capacities and quality of recording.

Minidisc (MD) recorders are currently popular with field recording as they are light, compact, reliable and have good sound quality. Some models have data reduction features, which, if possible, should be turned off (may decrease recording time per disc) as some think this can slightly damage recordings. This is more an issue for recordings for scientific analysis rather than general interest.

DAT recorders make some of the best quality digital recordings and unlike some MD recorders do not selectively record parts of the audio spectrum. However, some models can be unreliable in damp humid conditions and they can have a relatively high power consumption which normally can only be powered by a rechargeable cell, giving limited recording times in the field.

Solid state recorders are fast becoming the most widely used technology for sound recording in the field. The units can be as compact and even lighter than MD recorders. They can contain a fixed internal hard disk to store digital recordings or write to removeable memory cards (CompactFlash, SecureDigital etc), greatly increasing the recording capacities of a field unit. Many models can run on relativley low power and often take standard dry cell batteries. They usually have the choice of file formats to record - compressed formats such as MP3 should be avoided. Uncompressed formats (eg WAV) are preferred but take up much more memory, but with ever increasing memory card sizes this is becoming less of an issue.