This time of year there's always the same problem: are the birds you're
seeing the first northbound migrants or the wintering population?

Crude rule of thumb:
silent - wintering
singing - northbound migrant males (northbound males usually precede
northbound females in order to secure territory ahead of rival males).

Back East, in London ON, during the winter months we'd have winter robins,
Turdus migratorius, race nigrideus, always silent but for calls, but we
could always know when our Eastern Robin T.m migratorius, our breeding
species arrived about March 9, singing.

best, m