Bird migration evidence. Seabirds fly low over water but gain altitude when crossing land, and the reverse pattern is seen in landbirds. However most bird migration is in the range of . Bird strike aviation records from the United States show most collisions occur below and almost none above . Bird migration is not limited to birds that can fly. Most species of penguin (Spheniscidae) migrate by swimming. These routes can cover over . Dusky grouse "Dendragapus obscurus" perform altitudinal migration mostly by walking. Emus "Dromaius novaehollandiae" in Australia have been observed to undertake long-distance movements on foot during droughts. While participating
Not Only... But Also Dialogue", "A Spot of the Usual Trouble", that Cook was invited to become a permanent fixture and the show became "Not Only Peter Cook and Dudley Moore, But Also Their Guests", though it was only ever really referred to as "Not Only... But Also". This somewhat cumbersome title was later referred to by Cook in an interview as "another of Dudley's plodding ideas". Three series were made: January to April 1965 (prod/dir Joe McGrath), January to February 1966 (prod/dir Dick Clement) and February to May 1970 (prod/dir Jimmy Gilbert). John Street produced the (surviving) 1966 Boxing Day Special. The opening