Steampunk Seagull: I love the melody at exactly 0:15 (and the altered variation at 0:20) - that feels just right! The melody-instrument is a bit straining on the ear however, which is why the calm part at 1:01 (and 2:05 as it is looped) could have lasted a bit longer in my opinion - that could be quite nice. It does feel seagull-y (but maybe that is the image you have planted in my ear by the title xD)

Steampunk Seagull night: I like night themes that are just 'the main theme but softer'. Though I wish there was a bit more to it than the instruments being muffled - perhaps an instrument change to a soft instrument such as a piano-like or even xylophone-like. Maybe a small key change to a bit lower. Or lowering the tempo by a bit. I like what you got going on but, I'd say, experiment! :D

The technique of using major chords borrowed from different keys gives this song an uplifting feeling that feels relaxing. At the same time, the offbeat marimba notes highlight a non-diatonic minor tone that adds tension allowing for a satisfying resolution in the way that functional harmony would. I think that brass has a round or smooth quality which makes this a great fit for a song trying to evoke a more relaxed sound. Great job and thank you for sharing!

I definitely get the vibe. I like it a lot. 

I see what you're saying about the brass, it almost evokes bellows.