These are Darwin's finches -- similar birds with different beaks and so, different species. Darwin encountered them on his famous visit to the Galapagos and he writes:
The remaining land-birds form a most singular group of finches, related to each other in the structure of their beaks, short tails, form of body and plumage: there are thirteen species, which Mr. Gould has divided into four sub-groups...One might fancy that, and, of course, Darwin would go on to fancy that and more. But, while Darwin may be a saint of science, he is also an aesthete -- which is not unusual among scientists, I have found; many if not most of them know more about the arts than artists know about science. We saw him passing judgement on New Zealand a few days ago, and now there's this: "All the plants have a wretched, weedy appearance, and I did not see one beautiful flower." If he weren't so excited about the finches, you'd almost guess he was pouting.
Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.
But my favorite thing is the part about the tortoise urine:
When the tortoise arrives at the spring, quite regardless of any spectator, he buries his head in the water above his eyes, and greedily swallows great mouthfuls, at the rate of about ten in a minute... For some time after a visit to the springs, their urinary bladders are distended with fluid, which is said gradually to decrease in volume, and to become less pure. The inhabitants, when walking in the lower district, and overcome with thirst, often take advantage of this circumstance, and drink the contents of the bladder if full: in one I saw killed, the fluid was quite limpid, and had only a very slightly bitter taste.I have two reactions: 1. I'm sure Anthony Bourdain has done this already, and 2. Now you know why Coca-Cola was so popular when they started selling it around the world. I might also speculate that, once you've seen a man drink tortoise pee, it engenders a certain skepticism in the claims of his special divinity.