Any member of the Laridae family, Mouettes et Goélands;
More probably any unfledged bird.
10 occurrences (8 gull, 1 gulls, 1 gull-catcher)
ADO 2 3 118 p I should think this a gull,
TN 2 5 187 p Here comes my noble gull-catcher.
TN 3 2 66 p Yond gull Malvolio is turned heathen,
TN 5 1 205 p and a knave, a thin-faced knave, a gull?
TN 5 1 342 And made the most notorious geck and gull
1H4 5 1 60 As that ungentle gull, the cuckoo's bird,
H5 3 6 67 p Why, 'tis a gull, a fool, a rogue,
R3 1 3 328 I do beweep to many simple gulls,
OTH 5 2 164 As I have to be hurt: O gull, O dolt,
TIM 2 1 31 Lord Timon will be left a naked gull,
In Shakespeare's time, gulls must have been less numerous inland or on the coast, they kept to the sea as the pelagic birds they are. Man's modifications such as fisheries and rubbish dumps have since attracted them.
Even if the name of the bird came first, before the disparaging epithet, Shakespeare is more concerned with the meaning of gull as fool or simpleton. But on two occasions the reference to the bird is close. In 1 Henry IV we find "As that ungentle gull, the cuckoo's bird" (5 1 60) where gull clearly designates the young unfledged bird, here a cuckoo (see CUCKOO).
In Timon of Athens, the context is more elaborate:
When every feather sticks in his own wing,
Lord Timon will be left a naked gull,
Which flashes now a phoenix.
(2 1 30-2)
When a Senator wants his money back from Timon whom he despises because he is too generous, he uses the proverbial saying "When ....wing" (TILLEY, B375). With "feather" and "wing" the bird metaphor starts and is continued by "naked gull", a young bird without feathers yet.The Senator warns that it is Timon's last stand, that it "flashes now a Phoenix". With this intricate bird metaphor Shakespeare sums up his play up to this point, and gives a hint about the future of Timon.
In Twelfth Night, Fabian exclaims on the entry of Maria: "Here comes my noble gull-catcher" (2 5 187). And it is not to a kind of fowler that Fabian is referring, it is to a sharper. HARTING (p. 267) quotes Thornbury's Shakespeare's England: "The gull-groper was generally an old gambling miser, who etc".
There are not many references to seabirds in Shakespeare's work, but one can be found in Titus Andronicus, even if it is not precisely about gulls:
as a flight of fowl
Scatter'd by winds and high tempestuous gusts,
(5 3 69-70)