I'm going to answer this questions here for some of our other Young Fans even though I did visit with the Kinderchicklets (and Skye in Grade 1) on Wednesday.
McDermot's backpack is a satellite transmitter which is a bit like a cellphone. Every few hours, a satellite up in space calls McDermot's backpack to find out where McDermot is. It doesn't make noise or anything and McDermot can't tell, but the satellite calls the backpack and the antennae helps backpack to hear the phone call. The satellite then leaves a voicemail message for the researcher. Then the researcher "phones" the satellite and picks up the voicemail messages. It costs alot of money for the researcher to call the satellite, so they only call every couple of days. But when the satellite calls McDermot's backpack, it is a free call, McDermot doesn't have to pay anything!
The backpack is black on the top because inside the backpack there is a battery so the backpack has power to talk to the satellite - and the black part on top is a small solar panel to recharge the battery. If the battery couldn't recharge itself, it would wear out in a couple of days and the satellite couldn't call the backpack anymore. And if you tried to use a bigger battery, it would weigh too much and McDermot wouldn't be able to fly. It would be like a Kinderchicklet trying to pick up their Mummy or Daddy - much too heavy. If you count out 7 or 8 dimes, and hold them in your hand, that's how much the backpack weighs - not very much at all, which is important because even though peregrines look big, they are mostly all feathers and they don't weigh very much at all.
Sometimes the packpacks stop working, like toys at home or the tv or a car. If it breaks, then the satellite can't call the packpack anymore. If it stops working then when we (or someone else like us who watches over peregrines) will try to catch him and take his backpack off. If the packpack doesn't get broken, it will tell the researcher where McDermot goes during the winter and next summer and the winter after that and the summer after that and then maybe, where McDermot might find a lady friend and have a chicks of his own. Kinda cool.
The Peregrine Chick