Fictitious and Symbolic Creatures in Art, by John Vinycomb, , at sacred-texts.com
The Martlet (Merlette or Merlot, French; Merula, Latin). The house-marten or
as other birds do. It builds its nest frequently under the eaves of houses, from whence it can take flight readily, rarely alighting, as it gains its food while on the wing; the length of its wings and the shortness of its legs preventing it from rising should it rest on the ground.
It is depicted in armory with wings close, and in profile, with thighs, but with no visible legs or feet.
The martlet is the appropriate "difference" or mark of cadency for the fourth son. Sylvanus Morgan says: "It modernly used to signify, as that bird seldom lights on land, so younger brothers have little land to rest on but the wings of their own endeavours, who, like the swallows, become the travellers in their seasons."
The swallow (hirondelle) is the punning cognisance for Arundell. The seal of the town of Arundel is a swallow, Baron Arundell of Wardour bears six swallows for his arms. The great Arundells have as motto, "De Hirundine" ("Concerning the swallow"), and "Nulli præda" ("A prey to none"). A Latin poem of the twelfth century is thus rendered:
"We find it in Glovers’ roll," says Planché, "borne by Roger de Merley, clearly as 'armes parlantes,' although in a border." Roger de Merley: "barée d’argent et de goulz à la bordure d’azur, et merlots d’or en le bordure"; showing it was some difference of a family coat.