Behavior

The first glimpses of todies are invariably of diminutive, vivid green, rapidly bobbing birds uttering loud nasal beeps that are quite disproportionate to their size. Adults and children consider them cute, joining the company of old-time naturalists. For example, here is a quote from esteemed ornithologist Dr. Alexander Wetmore: "If there be gnomes and elves in our world of birds, among them are the tiny todies, whose long, spade-like bills, light eyes, brilliant plumage and peculiar mannerisms make them the dwarfs and hobgoblins of the West Indian forests...their acquaintance is one of the greatest pleasures that comes to a foreign ornithologist travelling in their haunts" (1927).

Although strictly territorial, todies temporarily join mixed species feeding flocks passing through their territories. This behavior is pronounced during autumn and spring, when migrating warblers (Parulidae) visit West Indian forests. Here, the avifauna is impoverished compared to that of the continental tropics, so flocks are small, often averaging only six species.

Because todies are among the smallest and most active feeders of all birds, it is only natural that they have evolved effective modes of conserving energy. They do not employ typical methods of keeping warm, such as group roosting and huddling. Instead they rely on internal physiological mechanisms. The Puerto Rican tody, for instance, exhibits a very low normal body temperature of 98.1° F (36.7° C), rather than the 104° F (40° C) typical of its relatives. This enables it to decrease its expected energy expenditure by 33%, reducing the body's demand for additional heat production.

Most birds are homeotherms, just like people. This means they maintain a constant body temperature with little fluctuation. The Puerto Rican tody exhibits a rare thermoregula-tory pattern in which its basic temperature varies widely. It can consciously control its normal body temperature by 27° F (15° C) from 82 to 109° F (28-43° C).

True torpor is relatively rare among birds. Todies not only exhibit torpor, but a controlled, sex-dependent, low metabolic rate that saves females approximately 70% of their daily energy expenditure.

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