It would not surprise me if they did subcontract out, although I do not know this for a fact. The no-update for days on end might be a clue.
In the past few years I've noticed a definite change in how easy it is to track packages. Some are straightforward, some have no updates for days and days on end (even shipping USPS Priority) including a regular box shipped priority to FL (expected 2-day per receipt) that took 11 days without updates for 6 six straight days!!! Also, if a package is transferred to UPS, then it can still be tracked. However, I have never personally shipped chicks.
Last year I did order chicks from Meyer (in OH and I live in OH, but they are approx 3 hours away). They shipped USPS in a specialty chick shipping box and the USPS tracking indicated Cleveland stop (as expected), but NO OTHER UPDATES until after they arrived at my PO and I got a call 2 days later around 6:30am. The update happened after I got my call. The chicks were all DOA and appeared to have been dead for the majority of their trip - the shipping material inside the box with the chicks was not disturbed, hardly any poops (and there were 26 chicks), the chicks were nice and warm (just dead)....leading me to believe whomever had them in their possession (USPS or subcontractor) placed them inside a truck with dry ice (suffocation) or blocked air holes (suffocation) due to how they were packed in the truck. Anyway, my suspicion is that they may not have been in USPS possession after Cleveland until they arrived locally.