upper is a female type mich with some traits reminding of cachinnans: slim bill with weak gonys and pointed tip, scap pattern (note dark streak along shaft, some rhomboidal structures), reddish tone to old coverts, diffuse (but hard to discern now) GC pattern. still, it is a michahellis: body structure, all black bill, conspicous dark streaking around eye, shorter legs, stronger subterminal mark on scaps than usually seen in cach and pattern on r6 (outer tail feather) clearly lead to a female YLG. note long wings in small female michs!
lower pic: adult and 2cy mich. the 1st cycle is pretty advanced with bold dark markings on a pale ground - "zebra gulls" as i like to call these types of cach and mich. note that it has replaced >95% of LC and MC and about 70% of GC which is quite advanced for a 1st cycle midwinter michahellis.