What passage, mate we can't see it?
In the morning is the adverb phrase.
It modifies the verb appeared as the phrase identifies when the birds appeared.
It is used in several contexts, one of them is "stark naked", when it is used like "naked as a jaybird", or in this case, when someone needs to take a shower, or change their clothes because she or he is scruffy, dirty or smelly, You may hear "go change your clothes, you are ragged as a jaybird", the color of the bird gives an appearance of dirt that is related to the popular saying.
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I need more information to answer this.. no paragraph has been provdided.