seagull 是不是可数名词

是的
给你举个例子
Seagulls were circling overhead.
海鸥在头顶山盘旋。

A seagull fluttered down with an injured wing.
一只海鸥拍打着翅膀飞落下来。

是可数名词

这几个例子里很明显啦

A seagull skims the water.
海鸥掠过水面。

A seagull fluttered down with an injured wing.
一只海鸥拍打着翅膀飞落下来。

Seagulls were circling overhead.
海鸥在头顶山盘旋。

A seagull hit the right wing tip, leading edge flap sustained minor damage.
右翼尖与一只海鸥相撞，前缘襟翼受到轻微损伤。

However, one seagull tried his best to keep the others off in order to let the broken-legged one eat first.
然而却有一只努力地驱逐别的海鸥而让一只断了腿的同伴先吃到食物。