Shorebirds are a group of birds belonging to the order Charadriiformes, but they are a distinct family from gulls. They are typically smaller, with longer legs and bills adapted for probing in sand and mud for food.
Here's the key difference:
* Shorebirds: Typically have long legs, short bills, and a more slender build. They forage by probing in sand or mud. Examples: Sanderlings, oystercatchers, plovers.
* Gulls: Have shorter legs, thicker bills, and a more robust build. They are opportunistic feeders, often scavenging or catching fish. Examples: Black-headed gulls, herring gulls, laughing gulls.
So, while a black-headed gull might be found on the shore, it's not considered a shorebird due to its distinct physical characteristics and feeding habits.