Songbirds
Explanation
The Joke
A man at what appears to be a bar or party tries a pickup line on a woman: "Hey girl, did you know that songbirds don't have penises?" She responds: "That's the worst pickup line I've ever heard." He continues undeterred: "Broadly, in fact, in the animal kingdom, the goal of female pleasure is recognized, and by other means..." She cuts him off: "I'm deducing that anyone who has to say so of female pleasure at a bar is incapable in bed." The final panel shows the same man trying the same opening line -- "Hey girl, did you know that songbirds don't have penises?" -- on a different woman, having learned nothing from the rejection.
The comic depicts a man who has latched onto an obscure zoological fact about avian reproductive anatomy and tries to use it as a pickup line, presumably to signal that he is knowledgeable and sensitive to female pleasure. The woman immediately and correctly deduces that anyone who needs to cite bird biology to impress women is probably compensating for a lack of actual romantic skill.
The Humor
The humor comes from the spectacular failure of using animal biology trivia as seduction, and from the man's complete inability to learn from rejection. The woman's devastating logical deduction -- that bragging about knowledge of female pleasure is itself evidence of incompetence -- is a sharp and funny observation. The final panel, showing him repeating the exact same line to someone else, confirms that he is trapped in a loop of clueless behavior. The comic also pokes fun at the "well actually" style of conversation where men share unsolicited scientific facts in social situations where they are profoundly unwelcome.
References
The zoological claim in the comic is essentially accurate: most bird species, including songbirds (order Passeriformes), lack a phallus. Only about 3% of bird species, such as ducks, geese, and ostriches, possess one. Birds typically reproduce via "cloacal kissing," a brief contact between the male and female cloacae.