#smilopterus

In the time of humans, guano was a valuable resource. These accumulations of excrement built over thousands of years were valued as fertilizer, as guano is rich in phosphates, nitrogen, and potassium. The deposits on this island, off the western coast of South America, were harvested first by indigenous Americans, then Spanish colonists. Industrial mining processes had destroyed the habitat of millions of seabirds, decimating their populations. Furthermore, guano miners had hunted birds and their eggs for food. On this stretch of coast, over 90% of the resident seabird populations were destroyed.

After 50 million years, both the birds and the guano accumulations have recovered. Seabird diversity was impacted both by the Holocene extinction and the later Angelean turnover event. Many seabird lineages managed to survive, however, and these survivors have radiated into the rich colonies that cover the rocks now. In the time of humans, the guano on these islands was primarily produced by cormorants, boobies, and pelicans. Now, the dominant seabirds here are petrels, bladewings, and diving-vultures. The composition of the guano, therefore, is slightly different than those 50 million years ago. It still retains its feracious value, but the last guano mine shut down ages ago.

But the guano wasn’t what this ottercat cared about. Swimming through the waters just offshore, she was more interested in the birds themselves, and the eggs they were sitting on. It was the middle of summer, peak breeding season for these birds. The majority inhabitants of this island were black-capped bladewings, streaked bladewings, yellow-headed diving-vultures, and South American lean-petrels. The ottercat’s ancestors, feral cats that lived in the urban parks of Lima, had preyed upon birds all the time, as part of their broad diets. After 50 million years, however, her lineage had adapted to a semiaquatic lifestyle. No longer were they the adept predators of small prey their ancestors were. A healthy bladewing would be too swift to ambush, and the diving-vultures and petrels could defend themselves. Instead, her goal was the eggs of the bladewings.

She leapt out of the water onto the rocky shore of the island and began climing her way up the rocks. Although most of the colonies nested on a near-vertical cliff face on the other side of the island, there were still many birds on this somewhat shallower slope. The footholds were still precarious, but this was nothing the ottercat couldn’t handle. Her paws had surprisingly strong grips, and she had successfully carried out egg raids on this island before. The lower edge of the colony area was occupied by bladewings, while diving-vultures claimed the top of the island. As she further ascended the island, one of the bladewings noted her presence. It let out a shrill alarm chirp, which set off the other bladewings. Many of the breeding pairs promptly deserted their nests, taking to the sky to save their own lives. A bird that flies away may nest another day. As an incessantly chirping flurry of the black-and-white birds ascended from the rock, they left behind hundreds of nests. Each nest was, at most, a simple depression in the guano, bearing two eggs each. All these eggs could be a feast for the industrious ottercat, who had the entire rock face to herself. Climbing up to a flatter rock face, she approached the closest of the nests. Her powerful jaws made short work of each of the eggs, which she ate whole. She could crush mollusks with her powerful jaws, eggs were no issue. Although bird eggs were not a staple of the average ottercat’s diet, the developing embryos inside were still a potential source of valuable protein. And with this many nests, the cost-benefit ratio could potentially be much higher than catching fish.

But the thing about climbing on guano-covered rocks is that one misplaced foot can upset your entire balance.

The ottercat placed her right front paw on a more loosely compacted ridge of guano. The ridge destabilized. Her reflexes could not grab onto more stable rocks in time. A number of bladewing nests crumbled with it and began sliding down the side of the islands with her. The guanoslide continued halfway down the side of the island until the ottercat slipped over a ledge and entered a brief freefall.

Smilopterus celer

Some lineages have not changed much in the past 50 million years of seabird ecological turnover. Petrels and gulls, for example, have not changed very much, and continue to fill the same niches as they once did. Other birds may seem to have not changed much, but do not be fooled. Bladewings may be compared to terns or tropicbirds, but those lineages are extinct; these Telogene birds are descended from modern gulls.