Post-Release Monitoring

Once an animal is released back into the wild it is not possible to routinely check up on how it is doing. Obviously it is important that we know how these animals integrate back into the wild, and we have been carrying out post-release monitoring for several years

BTO bird ringing

flipper tag

Tagging of seals

bird tag

Radio tracking

BTO Bird Ringing

The British Trust for Ornithology (BTO) runs the national bird ringing scheme (internationally recognised) which monitors bird populations, longevity, migration routes, etc. The RSPCA has adopted this scheme for rehabilitated birds.

We get valuable information, known as recoveries, from the wild (in the field) in a number of ways:

· Report of a bird seen alive, or found dead in the field.
· Bird ringers catching birds to record information about their condition.
· Birds readmitted to the Centre – from the BTO rings we know that some birds, particularly larger species, have been readmitted to the Centre. Some local swans have been admitted a number of times, often after a period of several years, for a variety of reasons, such as territorial fighting, injuries involving fishing line or hooks, oil contamination or lead poisoning.

Staff have to be trained and licensed to carry out bird ringing. The East Winch Wildlife Centre has been ringing swans since 1991. Kevin Leighton, one of our supervisors, is the Secretary of the RSPCA Ringing Group, covering 3 RSPCA wildlife centres.

Examples of sightings of swans:

· An adult mute swan ringed in October 1993, released near Ipswich has been back into care at the Centre in 2003 and 2005 – both times as a result of oil contamination. Its last recorded sighting was in December 2005, making it 12 years and 49 days after ringing – making it at least 14 years old.
· An adult swan admitted in 2003, released near Ipswich, has been sighted in the field a further 4 times – the last sighting was in March 2005
· Two mute swans cared for at the Centre in early 2003 (admitted from separate sites) were released separately in East Winch. In October 2004, ringers reported both swans at a site in Ely.

In 1991 we started to ring all birds – an interesting example of a recovery is:

· A tawny owl, admitted as an orphan and hand-reared at the Centre, was released in August 2001, near King’s Lynn. Over three years later it was admitted to the Centre, having fallen down a chimney. The bird was washed and then released again once recovered.

In 1996 we started to ring oiled seabirds. As a result of the ring returns we now know that there is a high mortality soon after release, and the RSPCA is now reviewing its protocol for these birds.

Colour Rings

Although we have been BTO ringing swans for many years, some questions are still unanswered, such as survival and dispersal of hand-reared mute swans. To try to find out more about what happens to these swans, in addition to the BTO metal ring, we started to use plastic colour rings on individuals. Each colour ring is inscribed with a unique alphanumeric code. These colour rings are more obvious in the field, making sightings of live birds easier. gull tag

The colour ring projects are registered, and at the Centre we use:

· Lime green rings with black lettering for swans (on either leg), and
· White rings with black lettering on the right leg for gulls (gulls with a white ring on the left leg are part of a Polish project)

There has been a marked rise in the number of sightings since these colour rings have been in use, such as:

· A black-headed gull, released in February 1991, was reported dead in May 1996. The information shows that the gull migrated 1,991 km north east, to Oulu in Finland, which is a natural behaviour, and that it survived for over 5 years.
· A hand-reared lesser black-backed gull, released near King’s Lynn in July 2004, was sighted in Iberia, having migrated 1,815 km – normal migratory behaviour as these birds winter in Spain.

Radio-tracking Tawny Owls

In 1994 we did a pilot study of radio-tracking of tawny owls, to assess their survival after release. We developed many new skills, including how to attach the transmitters to tail feathers, and which type of release aviary to use, and how many staff are needed to track the birds successfully. This trial was the forerunner of more recent tawny owl studies.

Each year the Centre hand rears a large number of bird, an average of 40 juvenile tawny owls are reared at the Centre. As tawny owls are the Centre’s most frequently hand-reared birds of prey, we were very keen to discover how well they survive after being released. We have just completed a 3-year project, starting in 2002, of radio-tracking juvenile hand-reared tawny owls. The results are encouraging and we are in the process of preparing a paper for publication.

The blackbird is one of the Centre’s most commonly treated garden birds, with an average of over 200 admitted each year. During the spring we often have recently fledged blackbirds brought to us. We are keen to find out whoe well these hand-reared birds integrate into the wild, and started in 2005 started a 2-year radio-tracking study to try to find out more.

Hedgehogs

We were involved with one of Pat Morris’s studies to try to find out how released hedgehogs integrated back into the wild. An individually numbered yellow plastic tag was super-glued to spines as a way of recognising the hedgehogs after release.

In May 2004 the Centre started to use small uniquely numbered tags – so far over 500 hedgehogs have been tagged in this way. The hedgehogs are released in gardens providing ideal hedgehog sites – natural shelter such as hedgerows, a log pile (which also encourages other wildlife), an overgrown wild area, or a man-made shelter (such as a piece of board against a pile of bricks to form a type of bivouac).

Although all the release sites offered supplementary feeding, only one group of hedgehogs have remained in the release garden – in an organic garden, with an area set aside to provide an ideal environment for hedgehogs.

Tagging seals

In 1988, after the Phocine (seal) Distemper Virus (PDV), we started to use small orange plastic tags in the rear flipper of seals. Each tag is uniquely numbered, and has contact details for London Zoo (Tel 0207 449 6671).

We have had a number of reported sightings of seals released by the Centre:

· A hand-reared seal pup was sighted in Aberdeen within a few days of release in The Wash
· A hand-reared seal pup was sighted in Holland within 7 days of release in The Wash

Radio-tracking seals

In 1995 we radio-tracked 5 hand-reared common seal pups. Radio transmitters were glued to their fur, on the back of their heads. The transmitters would fall off during the moult in August. The aim was to find out how these seals integrated with other seals, and how they survived in the wild. We planned to track them from a ship in The Wash, but sadly the seals vanished from range faster than we could follow them, and were never seen again.

We tracked them for a week following their release, but without any success.

However, since then, as with so many cases, science and technology has made vast and rapid improvements, and we are now able to use satellite tags to track animals released from the Centre.

Satellite Tracking Seals

Although we have had some interesting feedback from tagging our seals, we haven’t really found out much about how they behave in the wild. As well as location, satellite tracking records dive depth and dive time – this gives us an insight into how the seals are behaving.

In February 2004 we worked alongside the Sea Mammal Research Unit (SMRU) from the University of St Andrews in Edinburgh, to satellite track 6 common seal pups. The transmitters, which were glued to fur on the back of the head, would fall off during the moult in August.

The aim of the project was to find out if they survived and were able to dive as well as their wild peers. The preliminary findings are encouraging:

· A satellite-tagged seal swan across The Channel to Normandy
· Iimmediately after release the satellite-tagged seals only achieved short and shallow dives, but improved with longer and deeper dives

Staff has seen 2 of the satellite-tagged seals, one at Morston and the other in Kent. Both seals were within a colony of seals, looked fit and healthy, and when approached, moved off to a sandbank, with the rest of the colony. This is very encouraging.

Bernie McConnell of SMRU is preparing a paper for publication.

Current projects in post-release monitoring

Deer

Deer are released with a small plastic uniquely numbered tag in one ear. We have released almost 100 deer so far. However, we had had very few sightings. We hope that as the numbers of deer released with ear tags increases, we will have more feedback in the years to come. We would be very interested to have feedback of any sightings, even if the animal is dead, as this information is very valuable for rehabilitation in the future. Contact details are eastwinch@rspca.org.uk

A project of radio-tracking hand-reared roe fawns was started in 2005. Although we do not rear high numbers of these, we are particularly interested in how they survive once released.