Couple of things to try
Put the bird feeders in a big open area away from bushes where cats can hide.
Placing a 12 inch or so tall net fence around the area of the feeder. This way when the cat charges the birds on the ground under the feeder the cat must jump the fence before getting to the birds.
The mat shouldn't bother the birds. You can also use pointy twigs, or dried blackberry vines under the feeder.
The product "Shake-away coyote/fox urine" makes a cat deturent. Its a bit stinky and needs to be refreshed after rain. https://www.amazon.com/dp/B005VZYCPS/ref=cm_sw_r_cp_apa_glt_fabc_HW9BKE5KGJG7BFE360A7?_encoding=UTF8&psc=1
Good luck!
Kojotov urin u granulama Ne zezam se , bolje ovo nego da naškodiš mačkama https://www.amazon.com/Shake-5006458-Coyote-Urine-Granules/dp/B005VZYCPS#:~:text=Product%20description&text=Shake%20Away's%20patented%20formula%20uses,leave%20and%20avoid%20that%20area. Description This formula is incredibly effective in repelling domestic and feral cats.