Ornithologists love to study clutch sizes. Eggs are easy to count, and eggs are important-the more you lay, the more offspring you will have (provided, of course, that you can feed them and steer clear of predators). The name of the evolutionary game is to produce offspring, so there is intense selection on birds to optimize their clutch size. Thus the interest. For example, many dozens of excellent studies investigate the reasons why tropical birds lay small clutches (typically two eggs; their temperate zone counterparts often lay clutches of five or more!). I call myself an ornithologist, so it's no surprise that I've begun to study the clutch sizes of tropical birds. I recently teamed up with Andy Boyce from the University of Montana (and his labmate Adam Mitchell and advisor and breeding biology guru Tom Martin) to study how clutch size varies along the slopes of tropical mountains. We found that high elevation species lay smaller clutch sizes than low elevation species in three very different regions; the tropical Andes of Venezuela, the mountains of New Guinea, and Borneo's high peaks. It remains unclear why exactly high elevation tropical birds lay small clutches (often just a single egg!), but it is clear this is a general pattern. There is something about high elevation tropical environments that selects for small clutches, a new mystery for enterprising ornithologists to unravel. Read our paper at http://aoucospubs.org/doi/abs/10.1642/AUK-14-150.1, or email me for a pdf.