EMB ERJ 170/175 ER/LR
Distraction; Situational Awareness; Communication Breakdown
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Flight Crew Became Reoriented
Human Factors; Procedure
We pushed back from [the gate]... and started the engines after disconnect as usual. Upon both engines starting; we noticed the same push crew who had pushed us was in formation to marshal a plane into the gate we just pushed from. Normally this is the time we would run our after start checklist then call for taxi while stationary. However; trying to get out of the way to be courteous to the aircraft behind us; we ran the checklist as we were spinning out of the way to let them in. Because we were running a checklist and not thinking; we continued to taxi the aircraft to [the runway]. In our heads; and certainly with a lack of judgment; we were under the impression in our minds we had just communicated with ATC. As we crossed the non movement area line by about 100 ft; we stopped and noticed our radio was on tower and not ground frequency due to the radio call the tower gave us; 'aircraft taxiing...please identify yourself.' I identified our call sign and apologized that we had made the mistake of not calling for taxi instructions. We were in disbelief that we could do something so boneheaded and were embarrassed. It was just a mental mistake by the crew members. There was no safety at risk as we made sure the area was clear like we always do while the aircraft is taxiing. Because we have done this short taxi...a couple thousand times we got complacent and expected that was going to be our taxi instructions. Because we were verbalizing the checklist as we turned out; this was misconstrued in our minds as taxi instructions because that was the normal time to call and ask for taxi clearance. There are no excuses for our actions and it will be a learning experience to us to be sure all checklists are finished and proper communication established even though there might be somebody waiting on you.
[Report narrative contained no additional information.]
ERJ170 flight crew; distracted by a concern for clearing the gate for an incoming aircraft; failed to contact Ground Control prior to commencing taxi.