Here is some additional information from Dr. McGowan about tagging crows:

“Don't the tags and bands hurt the birds?

No. They are designed to be as innocuous as possible. Birds' "hands" are connected to their shoulders by a flap of skin (called a propatagium or simply patagium) that makes up the front edge of the wing. The flap is relatively thin, contains no muscle and only a few blood vessels. The tags are attached by a small piece of nylon sticking through the patagium. The ends of the nylon pin are melted to hold the tag on (with washers in place to decrease abrasion on both sides of the wing), and the tag sits on top of the wing. The tag does not interfere with any movement and does not pinch or rub any skin. Crows often preen the tags into place just like a feather. When I pierce the patagium to attach a tag the crow usually does not even flinch. They get more agitated when I measure their tail than when I stick in the pins.

 

Such obvious markers seem like they must increase the likelihood that predators will attack the crows or that other crows will shun them, don't they? To the best of my ability to detect it though, neither thing appears to be true. Unfortunately I cannot make direct comparisons on the survival of tagged and untagged crows because survival cannot be determined without marked individuals! I can say, however, that survival of tagged crows is extremely high. Fully half of all young crows that I mark in the nest are alive one year later. That may seem like a low survival rate, but in fact it is one of the highest known for birds! Breeder survival is on the order of 93% per year, again an incredibly high survival rate for birds.  (See McGowan 2001 for published survival rates.)

 

Crows with tags do not appear to be at any disadvantage in relations with other crows either. Again, it is impossible to have comparison data on unmarked crows, but tagged crows are accepted perfectly fine into their family units. They do not seem to be more involved than unmarked crows in fights and chases in big flocks (either as the pursuer or pursuee). And, they DO successfully compete for breeding spots. I have had over 75 tagged individuals successfully become breeders in my study.

 

No scientist manipulates their study subjects in any way without a great deal of thought and concern. Every researcher at a public institution in this country must have their proposed protocol approved by their Institutional Animal Care and Use Committee (my approved protocol number at Cornell is 88-210-04). But quite apart from the regulations and laws, good science requires that animals under study are interfered with as little as possible. And that is on top of the personal ethical decisions that each researcher must make about their comfort level with any action taken (or not). In my study I am interested in keeping the crows alive and visible, and if I knew that anything I was doing adversely affected the birds I would stop. I am fortunate to be able to state that the colleague who taught me the marking technique I use is very active in the Humane Society and People for the Ethical Treatment of Animals. Although I made my own evaluations, it seemed to me that her standards were likely to have been even more stringent than my own. I reasoned that if she was happy with the technique, then I probably would be too. And I have been.”