bank martin: swallow of the northern hemisphere that nests in tunnels dug in clay or sand banks
martin: any of various swallows with squarish or slightly forked tail and long pointed wings; migrate around Martinmas
ovulation method of family planning: natural family planning in which the fertile period is inferred from changes in the character and quantity of cervical mucus; ovulation is marked by an increase in mucus that becomes sticky and then clearer and slippery