You may be familiar with 'seagulls' - birds with webbed feet, white bodies, and grey wings - that are often found at the coast. However, there are various species that make up the gull family (and related birds). Gull identification is notoriously difficult, as the differences between species can be subtle and there are variations within species depending on the time of year and the bird's age. However, this Entry aims to give a few pointers about where to start when you encounter a gull-like bird.

Gull or Not Gull

According to the International Union for Conservation of Nature, there are 46 types of gull in the Larus genus. However, not all gulls are in this genus - there are 101 bird species with 'gull' in their common name.

Other birds with white bodies and grey wings include Terns, Fulmars and Albatrosses. These are not classed as gulls. Terns are slenderer than gulls, with longer, thinner beaks. Fulmars and Albatrosses are members of the Petrel family and are most often found out in the ocean.

Context

Before you even look at the bird itself, there are various contextual factors that will influence what it might be.

First is the season - gulls often have different coloured plumage depending on the time of year. For example, Black-headed Gulls have black faces in summer, but in winter they have white faces and black 'ears' (black feathers in small patches on either side of their heads).

The second factor is location - for example, in the UK a gull with a black face is more likely to be a Black-headed Gull than a Bonaparte's Gull, but Bonaparte's Gulls are common in Canada.

The third factor is situation - for example, is the bird on a cliffside, on a beach or further inland? Kittiwakes are more often found on cliffs (although they are becoming a common sight on bridges, for example in Newcastle, UK). Greater Black-Backed Gulls are likely to be found on beaches, while Lesser Black-Backed Gulls are often found on beaches alongside their larger cousins, but will also venture further inland.

Adult Features

Now we look at the features of the bird. Let's start at the top and work our way down, assuming that we're looking at an adult (juvenile gulls are even more difficult to identify than adults, as their speckled brown and white plumage is similar across species).

The first thing to check is how big the bird is. As their names suggest, the Great Black-backed Gull (Larus marinus) is the largest, and the Little Gull (Hydrocoloeus minutus) is the smallest.

Looking at the bird's head, there are several features to note. Firstly, is the head plumage white or does it include some black? Secondly, look at the beak. Several gull species have a yellow beak with a red spot, including the Lesser Black-backed Gull (Larus fuscus) and the Pacific Gull ((Larus pacificus). The Ring-billed Gull (Larus delawarensis) has a yellow beak with black ring. A Mediterranean Gull (Larus melanocephalus) has a red beak, while a Sabine's Gull (Xema sabini) has a black beak with an orange tip. Thirdly, look at the bird's eyes. A Mew Gull/Common Gull (Larus canus) appears to have an all-black eye, while other species have coloured irises featuring white, yellow and even red.

The colour of a gull's wings is most commonly a shade of grey, but can range from black to white depending on the species. Some species have black feathers at their wingtips while others do not. So-called 'white-winged gulls' include the Iceland Gull (Larus glaucoides) and the Glaucous Gull (Larus hyperboreus). Predominantly-black species include the Lava Gull (Larus fulginosus) of the Galapagos Islands and the Sooty Gull (Larus hemprichii) of the Arabian Sea coast.

Finally the legs and feet can be an identifying feature. As an example, the European Herring Gull (Larus argentatus) has a white head, yellow beak with red spot, grey wings and pink legs, while the Yellow-legged Gull (Larus argentatus) is very similar in appearance except it has yellow legs (as its name confirms).

If you are able to hear the gull, its voice may also help you to identify it. Calls range from the gruff 'uk uk' of the Great Black-backed Gull to the mewing of the Mew Gull.

Further Reading

Once you have noted the key features of the bird, browse a local guidebook or birding website, such as rspb.org.uk in the UK, to see if you can spot the species. A bird-identification app may help. Friendly people in a birdwatching group on social media or in nature reserves may also be able to provide advice. To develop your knowledge and skills further, you might like to subscribe to a birding magazine, as they often contain details of gull sightings and tips and tricks for gull ID. There are also in-depth books available, such as the Gulls of the World series by Klaus Malling Olsen, or Gulls: A Guide to Identification by PJ Grant, which contain information about juvenile plumage as well as identification of adult birds.