The Game Example on the rulebook posted on Kickstarter, on page 22 says:
"For his Branch Phase, Todd does what the four nightbirds tell him to do, to "Place  card from hand." He adds a three-nightbird card from his hand below the four-nightbird twig.
He then continues out along the branch and does what the three nightbirds tell him to do, to "Draw and add  cards." The twig is the same color as the other along his route on the branch, so the card is pumped up once, to "Draw and add  cards." (...)"
I couldn't find that rule about pumping same colored cards in the rulebook. Have I missed it somewhere? If so, what page? Otherwise, that rule might be missing.
This rule is on page 7, Bird Instructions paragraph. But you are right - it is not very obvious. It should be also in Branch Phase. I will contact the publisher and ask them to add it to rulebook.