In the 4th period of the calendar, in its last glyph (Ca7-24), the 'branch is broken': 

3			branch not broken
	Ca7-15	Ca7-16
4	branch broken
		Ca7-23	Ca7-24

Halfway through the cycle (which has 8 periods) waxing moon meets his end. Halfway through the year also waxing sun meets his end. Once we have understood that the cycle of the moon is more fundamental than the cycle of the sun several pieces of the puzzle are more easily understood.

I even dare project the black 4th quarter of the year back to it presumed origin, the moon cycle, and predict that we sooner or later will find evidence of the 4th quarter of the month being black too.

"... Although it belongs to the southern sky, the Corvus constellation remains visible in theory during the summer months, albeit very low on the horizon, even in latitudes where it passes unnoticed much more because of the length of the Arctic days than through its position in the sky ...

The Navajo ... who are Athapaskan from the north, and who have brought with them very archaic motifs ... in addition to the story of the 'split' twins ... were perfectly familiar with the Corvus constellation, of which they give the following analysis: 'feet far apart' (the irregular quadrilateral); 'his feathers'; 'his body'; 'his  stick'; 'his fire' ...

Even if north-west American Indians had been acquainted with the Corvus constellation and had given it a name, there is no reason why this name should have been the one that we have used since the times of the Greeks. This being so, it is all the more curious to discover among them myths which, without connecting the bird with a constellation, tell a story about it which is almost identical with the one current among the Greeks to explain the origin of the Corvus constellation:

M593. Takelma. 'The thirsty raven'

There was no water in the village. The lakes and rivers were dry. Raven and Crow, two young girls who were having their first menstrual courses, were told to go and draw water from the ocean. Finding the journey too long, Raven decided just to urinate into her basket-bucket. She decieved no one and was severly scolded. Crow returned much later but with drinking water.

As a punishment, Raven was condemned never to find water in the summer; only in winter would she find something to drink. For that reason the Raven never drinks during the hot months; she speaks with a raucous voice because of her dry throat ... (The Naked Man)

According to Allen: "... the bird, being sent with a cup for water, loitered at a fig-tree till the fruit became ripe, and then returned to the god with a water-snake in his claws and a lie in his mouth, alleging the snake to have been the cause of the delay. In punishment he was forever fixed in the sky with the Cup and the Snake; and, we may infer, doomed to everlasting thirst by the guardianship of the Hydra over the Cup and its contents. From all this came other poetical names for our Corvus - Avis Ficarius, the Fig Bird; and Emansor, one who stays beyond his time; and a belief, in early folk-lore, that this alone among birds did not carry water to its young ..." If, as I suspect, Corvus equals GD11: then he may be the summer solstice solar bird. The one who stays beyond his time, Emansor, is a suitable name for sun at solstice. If he delays until fruit ripens, then his season may be longer than that, though figs perhaps ripen just after summer solstice. Sun is high in the sky - he must be a bird - and the heat makes people thirsty.

The menstruating girls suggest the moon, maybe one of them (Raven) was waxing moon and the other (Crow) the waning moon?

The Fig Bird blamed the snake (2nd quarter) while waiting for the fruit (hua) to ripen. The fig tree parallels Rakau.

I searched through all 101 manu rere glyphs in Tahua and without question the 4 redmarked below are exceptional in pointing skywards with their beaks:

Aa3-49	Aa3-50	Aa3-51	Aa3-52	Aa3-53	Aa3-54	Aa3-55	Aa3-56
Aa3-57	Aa3-58	Aa3-59	Aa3-60	Aa3-61	Aa3-62	Aa3-63	Aa3-64

Is it the thirsty beak we see at left in Aa3-50 (manu kake)?

The importance of the moon cycle may be due to the tides:

"... Raven, the demiurge and trickster, was able to escape from the rising waters by 'flying to the highest cloud in the sky, and hanging on there by his bill'.

There is indeed an unusually sharp hook at the end of the bills in the red-marked manu rere glyphs.

When the waters had subsided, he came back down to earth and arrived at the house of an old woman who was mistress of the tides. She could not believe her eyes when she saw that he had sea-urchins to eat, because at that time the tide was always high and sea-produce could never be harvested since the waves never went back.

Angered by his hostess's incredulity, Raven stuck the spikes left over from the sea-urchins into her body and commanded the sea to withdraw: 'Finally everything became dry - this was the lowest tide that ever was. All kinds of salmon, whales, seals and other creatures lay on the sand flats. People collected enough from that ebb tide to last them for a long, long time.' This is the origin of the tides ..." (The Naked Man)

At high tide, I suppose, with no food to collect from the sand flats, people should instead be occupied with celestial matters.

Twice a day the clock of the tides cycled around, and without doubt ancient peoples understood it was on order from the moon ('the old woman who was mistress of the tides').

"... The various frequencies of orbital forcing which contribute to tidal variations are called constituents. In most locations, the largest is the 'principal lunar semidiurnal' constituent ...  Its period is about 12 hours and 25.2 minutes,exactly half a tidal lunar day, the average time separating one lunar zenith from the next, and thus the time required for the Earth to rotate once relative to the Moon. This is the constituent tracked by simple tide clocks ..." (Wikipedia)