Seagull does have an important environmental message but it does not feel too didactic.
The seagull is caught in some discarded fishing line. The more she struggles the worse she becomes tangled. Seagull enlists the help of others - a mullet, a pelican and a crab. Each tries but can only loosen it a little. Then comes the important turning point :
"Soon Seagull was too exhausted to move any further. She nestled in among some tall grass at the edge of the dunes and closed her eyes. The setting sun looked on. Through the half light Seagull heard footsteps."
Aside from the gentle story and lyrical language I really loved the illustrations in Seagull especially the full page which shows the pelican.
If you are exploring an environmental theme with a class of younger students make sure you add Seagull to your book collection.
Here is a set of teachers notes. You might also enjoy Samantha Seagulls Sandals by Gordon Winch and Peter's Place by Sally Grindley.