Isbthis a blackcap

Hello I wonder if anybody could help me please.  I am baffled.  I am usually good identifying burd song calls but this one has stumped me.  We walk our dogs along the South downs with lots lots of woodland.  We have seen this bird which looked like a blackcap.  It was a small bird with a dark head.  It's call sounded like it's saying TWIT.  That's it.  A bit of a pause then TWIT again.  I've checked my bird call app and nothing on there helps.  Do male females have different calls?  Could anybody please help me.  It's driving me crazy haha

  • We had a walk along our local canal yesterday and most of the bird noise we heard was more in line of contact calls or "feed me" requests from late fledglings. There was one Chiffchaff that seemed to be trying out its new voice with mixed results A pair of Common Terns were going frantic over the presence of Corvids in their area we presume they still have young in the nest. Despite thst it is still a quiet time for birds and better trying to i.d. butterflies and damsels and dragons