Green’s Dictionary of Slang

lark n.³

(US) a fellow, a man.

1822		Commercial Advertiser (N.Y.) 14 Nov. 2/2: We observed [the pickpocket] a few minutes before nibbling at our pocket; but being at the moment much interested in [the play], and knowing that as usual, there was nothing in it but a few old papers, and an article about South American news, we suffered him to work away unmolested — but in three or four minutes afterwards, Hays had the brisk lark by the shoulder.
1824		National Advocate (N.Y.) 7 June 2/2–3: ‘Stop awhile,’ said the Captain of the Watch, ‘I have some small grievances which I desire to specify against this lark here. [...] It seems this lark has just arrived from New-Orleans.’.
1835		W. Otter Hist. of My Own Times (1995) 119: Her intended husband, and he was a sweet looking lark.

SE in slang uses

In phrases

have larks for breakfast/supper (v.) [larks are trad. good singers]

(Ulster) to be especially eloquent.

1902		Eve. Teleg. (Dundee) 28 Feb. 4/3: We cannot always get the abstract best [...] We cannot always have larks on toast and breakfast in bed.
1913		A. Irvine My Lady of the Chimney Corner 148: ‘Ye’ve had larks for supper, Billy; yer jokin’!’ Jamie said. ‘Larks be d--d,’ Billy said, ‘m’ tongue’s stickin’ t’ th’ roof ove me mouth!’.