There is a parameter available called _sort to specify the field but I would like to understand what is the default sorting parameter when we retrieve list from any of the resources in HL7 FHIR.
I have compared the ID and read the documentation. There is no luck.
FHIR does not dictate how a server should sort, so it will depend on the server implementation.
Servers are supposed to indicate their sorting in the self link (see http://hl7.org/fhir/search.html#conformance), and to honor the _sort parameter when that is on the request.