How Many Fish Can a Puffin Carry? The Bill-Load Record

Why puffins carry fish in their bills

Most seabirds that feed chicks far from the nest swallow their catch and bring it back up at the nest. The Atlantic puffin does something different: it brings whole fish home in its bill, lined up side by side with heads and tails dangling on each side.

This lets a parent make one foraging trip count. Instead of returning after every catch, it can keep diving until its bill is full, then fly back to the burrow with a load that may represent many dives. The chick, called a puffling, simply swallows the fish whole once they are dropped on the floor of the nest chamber.

Puffins only collect bill-loads when they have a chick to feed. When feeding themselves, they swallow small fish underwater, and an adult needs roughly 40 small fish a day.

How a puffin’s bill holds so many fish

Three features of the bill and mouth make large loads possible:

• A spiny palate. The roof of the mouth has rows of small, backward-pointing spines.
• A rough, muscular tongue. The grooved tongue presses each fish against those spines, holding it in place.
• Hinged jaws. The upper and lower halves of the bill can close parallel to each other along their length, not just at the tip, and their edges have small serrations.

Together these let the puffin hold the fish it has already caught while opening its bill to snap up the next one. The bill grows larger and deeper in the breeding season, with colorful outer plates, but the gripping system works the same way. More on the seasonal bill is in Why do puffins have colorful beaks? Birds do not have true teeth, and spines and serrations like these are one way they make up for it, as explained in Do birds have teeth?

What decides the size of a load?

The number of fish in a bill-load varies far more than its weight. A load might be one or two larger fish of 10 cm (4 in) or more, or several dozen tiny ones only a few centimeters long. Researchers who study puffins usually weigh loads as well as count them, because the total amount of food matters more to the chick than the number of fish.

Several factors affect what a parent brings home:

• Prey size and type. Young-of-the-year sand eels and fish larvae are small and numerous, while older sand eels, herring and sprats are bigger and fewer per load.
• Distance to feeding grounds. When fish are close to the colony, parents tend to make more trips with smaller loads; when they must fly far, they bring bigger loads less often.
• Food supply that year. In poor years, loads are smaller and visits less frequent, and chicks grow slowly or starve.
• Thieves. Gulls and Arctic skuas chase puffins to make them drop their fish, so a parent may lose a load before it reaches the burrow.

The 62-fish record

The figure of 62 fish in a single bill is repeated in many books, guides and visitor centers, usually credited to a puffin in Britain. It has become the standard “record”, but it comes from an individual observation rather than a systematic study, so it is best treated as an exceptional maximum. Loads of 20 to 30 very small fish are seen from time to time at colonies when tiny prey is abundant.

What matters for puffins is not the record but the typical load. Long-term studies at colonies such as the Isle of May in Scotland show that load weight and fish quality change from year to year with the food supply, and that these changes are closely tied to how many chicks fledge.

What fish do puffins bring to their chicks?

Chicks are fed slender, energy-rich schooling fish, usually 3–10 cm (1–4 in) long. The main prey varies by region:

The quality of the fish matters as much as the number. In poor years in Maine, parents brought in butterfish, which are deep-bodied and often too wide for a young puffin to swallow, and many chicks starved beside uneaten food. In Shetland, years with few sand eels led to near-total breeding failure.

How often are puffins fed?

Both parents bring food, and a chick typically receives several bill-loads a day, more in good years and fewer when fish are scarce. Feeding grounds can lie many kilometers from the colony, and parents often arrive back in groups, which helps reduce theft by gulls and skuas.

The chick grows quickly on this diet, putting on roughly 10 g (0.35 oz) a day at first. After about six weeks it leaves the burrow at night and heads to sea, where it must catch its own fish. Other diving seabirds, such as penguins, feed their chicks by regurgitation instead; see What do penguins eat? for how their diets compare.