Unfortunately, one of their favorite activities while roaming around includes killing a large number of birds[1]. While some may scoff at that, birds (even the ones considered less desirable) contribute to lowering the populations of insect pests that would annoy us or eat our crops. China nearly wiped out the common house sparrow in the 1960s and it helped lead to The Great Famine[2] as the sparrows ate much more insects than they did grain. Many types of the less invasive bird species also do not reproduce nearly as fast or in abundance as their feline predators. So while cats might have a few litters or more each year, the birds they are killing might only have one successful clutch, if that. Unlike mammals, most bird species also need both parents to raise their young. If one is killed, the other will most likely abandon the nest.<p>Countries like New Zealand[3][4] have had to worry about the size of cat populations lately just to keep birds like the kiwi from being wiped out. New Zealand originally had no native mammals and the birds there have not yet built up a sense of fear to them (or even us) in many cases. Although cats are a guilty party, we also did some damage by wiping out some unique New Zealand species, such as the Moa[5]. Until mammals came along, birds were the dominate species of the island, which is one of the factors that makes its ecosystem so interesting to study.<p>[1] <a href="http://www.npr.org/blogs/thetwo-way/2013/01/29/170600655/behind-cute-face-a-cold-blooded-killer-study-finds-cats-kill-billions-of-animals" rel="nofollow">http://www.npr.org/blogs/thetwo-way/2013/01/29/170600655/beh...</a><p>[2] <a href="http://en.wikipedia.org/wiki/Four_Pests_Campaign" rel="nofollow">http://en.wikipedia.org/wiki/Four_Pests_Campaign</a><p>[3] <a href="http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10860618" rel="nofollow">http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objecti...</a><p>[4] <a href="http://www.telegraph.co.uk/news/newstopics/howaboutthat/8021992/Deodorant-sought-to-save-New-Zealands-smelly-birds.html" rel="nofollow">http://www.telegraph.co.uk/news/newstopics/howaboutthat/8021...</a><p>[5] <a href="https://en.wikipedia.org/wiki/Moa" rel="nofollow">https://en.wikipedia.org/wiki/Moa</a>
I wonder what kind of equipment they use. I can't imagine strapping a Raspberry Pi to my cat to find out what he's up to. Do they use custom built hardware?