How safe is mist-netting?

[John Chardine]

A standard technique in field ornithology is to trap birds in "mist nets". These are gossamer nets into which the bird flies and becomes trapped. Workers patrol the nets and remove the birds, which are then typically banded/ringed, measured, sexed, and let go. Mist-netters are highly trained individuals who, in North America at least, have to hold at least three permits (bird banding, scientific and animal care), and likely others if they are working in a reserve. Mist-netting is a very valuable technique that has resulted in the accumulation of a huge bank of knowledge that is used to conserve birds.

People who don't understand the technique look from the sidelines and assume it is injurious to birds. In fact it has been said here at BPN that all birds caught in mist-nets are injured. It is well known in ornithology circles that this is not the case but the definitive study had not been done, until now (see the link below). The study found that a very small proportion (about 0.5%) of birds are injured due to mist-netting but the associated injury does not seem to affect future survival based on recapture rates.

In case you feel that ANY injuries are unacceptable, it should be understood that almost no intervention used by field biologists is without risks to study organisms. In the permitting process, risks are weighed against benefits and high-risk/low benefit studies are simply not allowed to proceed. All good field biologists understand the need to minimise risks to study animals and maximise the benefits of the study, and this is supported and regulated by a strong permitting system in most places. If we were completely intolerant of risk to wildlife caused by field research we would know little about the living world around us and would be in no position to manage, conserve, and preserve wildlife populations, including critically endangered species.

Here's a short write-up of the study:

http://www.sciencedaily.com/releases/2011/06/110629203014.htm

[Jeff Cashdollar]

John,

Thanks for the article. I must confess I see both sides of the equation but firmly agree the data is critical. Just as our species has benefited from the data collection (different processes). Does the end justify the means and IMO it does. In your option, do you feel we sometimes over study birds. Moreover, when I see birds with three or four bands sometimes it makes me pause. I am very supportive of the science and all that you do. To me it also shows you care about birds. Without the care, there is no science - thanks.

[Paul Guris]

John,
Moreover, when I see birds with three or four bands sometimes it makes me pause.

Just as an FYI, a recaptured bird does not receive another band. Any bird with multiple bands has been marked that way for a specific reason, usually so visual ID can be made of the specific individual. Biologists use unique combinations of multiple bands of different colors in different positions on the leg to do this.

Much of what we know of the familial interactions of highly intelligent and social birds, such as jays and crows, comes from this work. For example, this technique is used to study the uncommon, very localized, and highly vulnerable Florida Scrub-Jay. It is also done on shorebirds in the East to determine what feeding areas individual birds are using, without having to retrap them to read their bands.

[John Chardine]

Hi Jeff- Thanks for your comments and good comments from Paul. Over the years I have routinely colour-banded seabirds with three colour-bands and one metal band. With 6 colours to choose from you can imagine all the combinations available so each individual can get a unique combination. I typically put one colour above or below the metal band on one leg and two colours on the other. Birds with longer legs (e.g., shorebirds) can take more bands. The internal diameter of the bands and the height are all gauged so that they fit perfectly with no chaffing. I have worked with birds that have had their bands on for 20+ years. Bands do cause the occasional injury but it is very rare mainly because in most parts of the world banding is strictly regulated.

As an aside, banding with a single metal band that can't be read without having the bird in the hand has been used for a long time with millions of birds tagged and released. This has produced a huge database of information on movements, survival rates etc. More recently though, we are using small loggers attached to the band itself. These loggers measure light levels and time, from which you can work out latitude and longitude to about 100 km accuracy. This gives you the track a bird takes over the course of a year rather than just an endpoint obtained from a band recovery. This has caused a huge revolution in the science of animal movement.

[Linda Dulak]

There is another technique that is used for shore birds. I'm not sure how they are captured and banded, but they carry flags with numbers that can be read at a distance. I've attached an image of a red knot taken this spring on the Delaware Coast. This is a large crop from an image of a mass of birds on the shore. It was submitted to document this bird position on that day. I've wondered if these flags do have any adverse effect on the birds.

Linda

[Norm Dulak]

John.

I think that data obtained through mist-netting are important, even though there may be some risk to individual birds. Only by knowing where the birds go as they carry out their lives can we have any hope of preserving habitats essential to their survival.

As the human population continues to expand, we can only hope that some space will be preserved to allow our feathered friends to live together with us. The data obtained through mist-netting may make that possible.

Norm

[John Chardine]

Hear hear Norm.

Linda- great to see the flag. Flags like this have been used for a long time and there is no evidence that they have any negative impact on the birds. They are a good alternative to using several bands. We also use single engraved colour bands but the letters have to be really small on most small shorebird bands, and they have to be viewed often from a distance so the flags work better.

[Eric Weaver]

Some good information for this eager but fledgling birder. Thanks for the post. I have so much to learn and this forum has become a great starting point for me.

[John Chardine]

Following on from the mention of loggers, here is perhaps the archetypal study to-date using loggers to track the migration of the Arctic Tern. It gives you an idea why I said this technology has been revolutionary.

http://www.arctictern.info/

[Rick Poulin]

John the info on the Arctic Tern's is fasinating. It would be very interesting to see the path of the Arctics that use an inland route. We get Arctic Terns every year here in Ottawa at the end of May early June.