▁. ▁ ▁It ▁bre eds ▁in ▁southern ▁Europe ▁across ▁ ▁Central ▁Asia ▁to ▁northern ▁China . ▁This ▁species ▁is ▁strongly ▁mig rat ory , ▁all ▁populations ▁winter ing ▁in ▁Africa ▁south ▁of ▁the ▁Sah ara . ▁It ▁is ▁an ▁un common ▁visitor ▁to ▁northern ▁Europe . ▁Its ▁range ▁has ▁contract ed ▁somewhat ▁at ▁the ▁peri ph ery ▁in ▁recent ▁dec ades ▁due ▁to ▁habitat ▁destruction . ▁For ▁example , ▁in ▁the ▁early ▁ 2 0 th ▁century ▁it ▁b red ▁in ▁the ▁J ura ▁Krak ow sko - C zę st och ow ska ▁( Pol and ) ▁where ▁none ▁occur ▁today , ▁but ▁it ▁is ▁not ▁considered ▁glob ally ▁end anger ed . ▁ ▁Description ▁This ▁is ▁a ▁medium - s ized ▁but ▁stock y ▁thr ush ▁ 1 7 – 2 0   cm ▁in ▁length . ▁The ▁summer ▁male ▁is ▁un m ist ak able , ▁with ▁a ▁blue - gre y ▁head , ▁orange ▁under parts ▁and ▁outer ▁tail ▁fe athers , ▁dark ▁brown ▁wings ▁and ▁white ▁back . ▁Fem ales ▁and ▁imm atures ▁are ▁much ▁less ▁striking , ▁with ▁dark ▁brown ▁scal y ▁upper parts , ▁and ▁pal er ▁brown ▁scal y ▁under parts . ▁The ▁outer ▁tail ▁fe athers ▁are ▁re dd ish , ▁like ▁the ▁male . ▁ ▁Be hav iour ▁and ▁e col ogy ▁ ▁This ▁species ▁bre eds ▁in ▁open ▁dry ▁h illy ▁areas , ▁usually ▁above ▁ 1 5 0 0   m . ▁It ▁n ests ▁in ▁rock ▁cav ities , ▁lay