Every card in a Lenormand deck carries a small inset of an ordinary playing card in one corner, and the Birds carries the 7 of Diamonds.
Why the deck has thirty-six cards
Taken together the insets across the deck make up a complete thirty-six card playing pack, running from the six to the ace in each of the four suits. That is not a correspondence scheme laid over the pictures afterwards. The deck was published in Nuremberg in 1799 as a race game called Das Spiel der Hoffnung, the Game of Hope, generally attributed to Johann Kaspar Hechtel, and the insets meant the same printed sheet could be cut up and used for ordinary card games as well. The pictures were the board and the playing cards were the pack.
What the suit adds
The 7 of Diamonds belongs to the suit this atlas records under money, work and the material. It is a pip card. In playing card cartomancy the numbered cards are generally read as circumstances rather than as people, and the number is read alongside the suit.
Why a single card is rarely read alone
Lenormand practice reads cards in pairs and in the Grand Tableau, the layout of all thirty-six at once, rather than drawing meaning out of one card in depth. A card is modified by what sits beside it, and the same card in two positions is two different statements. That is the sharpest difference between this system and tarot reading, and it means the playing card inset is one more thing a reader may or may not bring to a combination.