How big are elegant terns?

Elegant terns (Thalasseus elegans) are medium-sized seabirds that belong to the family Laridae. They are found along the coastlines of temperate and tropical oceans worldwide. Elegant terns are known for their graceful flight and aerial agility. Their size can provide some insights into their ecology and behavior.

Body Size

Elegant terns have a body length of about 36–41 cm (14–16 in) and a wingspan of about 76–91 cm (30–36 in) (Reference 1). Their overall size places them in the medium range for terns. Some key body size measurements for elegant terns are:

As the table shows, elegant terns are relatively lightweight birds, tipping the scales at just 110–170 g (3.9–6 oz) (Reference 2). Their medium size and light weight allows them to fly gracefully and dive for fish.

Size Differences Between Sexes

There is some sexual dimorphism when it comes to size in elegant terns. Males tend to be slightly larger than females in their body measurements.

Some key size differences include:

As you can see, males tend to be 2-3 cm longer in body length and have wingspans about 10 cm greater than females. They are also around 30 grams heavier on average than females (Reference 3). The size dimorphism is thought to allow males to dive deeper and fly higher when provisioning females and chicks.

Size Through Seasons

The size of elegant terns changes over the course of the year as they molt and fatten up for breeding.

In winter, their weight drops to about 100-140 g as food becomes scarcer. However, as breeding season approaches, their weight increases to 130-170 g to provide energy for courtship, nesting, and chick rearing (Reference 4).

Their wingspan also increases slightly just prior to breeding season. This seasonal variation allows them to conserve energy in winter while maximizing flight performance for diving and fishing when breeding.

Size Relative to Other Terns

Compared to other tern species, elegant terns are medium-sized:

The elegant tern is smaller than the largest terns like the Caspian tern, but larger than petite terns like the least tern. Its medium size allows it to nimbly fly and dive for fish. Larger terns tend to go after bigger fish, while smaller terns eat more invertebrates.

Bill Size

The bill size of elegant terns is medium-sized and specially adapted for catching small fish:

Their bills are pointed and lack the heavy keel of larger piscivorous birds. This slender, medium-length bill helps elegant terns snap up fish and insects (Reference 5).

Leg Size

Elegant terns have short legs set far back on their body to provide propulsion for swimming and diving. Their exact leg measurements are:

Their short, strong legs allow them to float atop the water and dive from the surface pursuit of fish. Their feet have webbed toes for paddling and swimming after prey.

Facts About Elegant Tern Size:

• Elegant terns have a wingspan of 76-91 cm and weigh 110-170 g
• Males are slightly larger than females in body and wingspan
• Size increases prior to breeding season then decreases in winter
• Elegant terns are medium-sized compared to other terns
• They have pointed, medium-length bills for catching fish
• Their short legs help them float on the water and dive for prey

Conclusion

In summary, elegant terns are medium-sized seabirds well adapted for an aerial, piscivorous lifestyle. Their measurements of 36-41 cm length, 76-91 cm wingspan, and 110-170 g weight provide information about their ecology, behavior, and place relative to other terns. Males tend to be slightly larger than females, and their size fluctuates through the seasons as they molt and fatten up for breeding. Elements like their bill and leg size reveal nuances of their adaptation for plunge diving after fish. Knowledge of the size of elegant terns sheds light on how their morphology supports their role as agile, fish-eating seabirds.