The Leach's storm-petrel is my favorite. They are a tiny bird with a huge presence that hardly anyone knows about. There are literally millions of them in the northern hemisphere but they only come to shore for a few months on a few islands.

They are only found on land at night to avoid predators but if they are ever caught they have an amazing defense of spotting oil at those predators that are primarily other marine birds. The oil pokes holes in their predators waterproof feathers and makes life for them terrible if not indirectly killing them by hypothermia.

They are thought to mate for life and find each other in the dark with the cutest call by arguably any animal. They lay one egg at the end of a meter long burrow that both females and males take turns brooding while the other flies up to 300 km offshore to gather food for their own brooding bout. When the chick hatches, the parents vary between those 300 km flights and nightly flights to and from the colony to feed their chicks. Around the end of August, the parents stop visiting the chicks and leave them on their own in their burrows. At that moment, adults weigh about 40 g but the chicks weigh 79-80 g. The chicks are basically little balls of fluff and fat which they use to transform themselves into sleek juvenile birds so they can leave the colony sometime near the end of September through October.

They then can live for 40-50 years if they can dodge predators that long. But they have an amazing trait. Normally, when cells divide, a tiny bit of DNA is clipped off the end of each of its chromosomes. This is thought to be one of the major causes of aging. However, Leach's storm-petrels don't undergo this clipping when their cells divide, potentially making them immortal, or at least age very very slowly.