Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 150
Confusion; Communication Breakdown; Physiological - Other; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway; Ground Incursion Taxiway
Air Traffic Control Issued Advisory / Alert; Aircraft Aircraft Damaged; Flight Crew Became Reoriented
Procedure; Human Factors; Environment - Non Weather Related; Staffing
Operating flight from ZZZ to ZZZ1. After landing on Runway XX; exited on Taxiway A and turned left on Taxiway C; and believing that Tower had actually cleared us to taxi to the gate; we started to slowly taxi; when Tower called us and asked that we call Ground. We called Ground and he stated 'You started to taxi without calling us; and crossed Runway XX; which is an active runway'. We had barely started to taxi on C. We had read the NOTAMs; and in fact; Runway XX was 'NOTAMed CLOSED'; so it could not be an 'Active' at all. Regardless; we asked Ground for taxi clearance to the gate; and received clearance to the gate via 'C.' We did not want to argue with the Ground Controller; but we do know that Runway XX is Closed at ZZZ1; so it's not Active in any way. We asked the Ground Controller if we should 'expect any paperwork'; and he said 'no'. I do not believe we did anything wrong; but it's better to be safe and proactive; and learn from our possible mistakes.We had flown into ZZZ1 previously (a few days before) and due to controller shortages or consolidation of ATC positions (During COVID-19 times); the Tower normally gives us the taxi instruction after we cleared the landing runway. This time; we cleared the runway and thought we had heard the Tower tell us to 'taxi to the gate' (as they have been doing recently). We started to slowly taxi on Taxiway C and that's when Tower asked us to 'call ground for taxi;' something they had not done in the past 3-6 times we had landed there recently. So; probably I was expecting the same ATC procedures to happen; but regardless; in the future; will come to a stop on the taxiway and not move until further taxi clearance is received.I would suggest to avoid being complacent; and instead of expecting the same type of ATC handling from small airports as we may be getting every day during COVID-19 (combined controller positions; where there is perhaps combined Tower and Ground; or even Approach/Tower/Ground Controller); and instead treat it just like a busy airport.
Air Carrier Captain reported a taxiway/runway incursion and cited ATC staffing; local ATC procedure change and confusion over a NOTAM contributed to the deviation.