Pires, the lone choreographer who opted for the first road, opened the bill with “Auspicy” (which means taking omens from the observation of birds), an intensely collaborative narrative entry with the design duo Viktor & Rolf. The ballet started with a visual bang, as the curtain rose on a towering, gilded shell. Dancers in bronze unitards with neck and wrist ruffles emerged from the folds of this gargantuan, lamé Mother Ginger, summoned by a flute trill. Listed in the program as Offspring, Fledglings, and Community, these sleek, tufted creatures were a cross between “Nutcracker” Polichinelles and Brancusi’s Space Birds. Much of the perky partnering choreography for the Offspring, Emma Von Enck and David Gabriel, evoked the harlequin clowns Pierrot and Pierrette.

Unity Phelan, as Mother, appeared in a huge golden gown with “P-R-O-T-E-C-T” floating across her shoulders like candles on a cake. I thought of the various titles, arrows, or commands that hover over players in video games. She was a walking billboard—walking being the operative term. There was not much she could do in that bulk other than stroll or bourrée through her flock from time to time. But when the curtain began to fall a few minutes into the ballet, she ran to stop it—a moment so startling it seemed like perhaps it was an accident. Many in the seats around me whispered to each other, “was that supposed to happen?”

Midway through the dance, Phelan gifted long feather tails to Von Enck and Gabriel, who burrowed into her. They had apparently leveled up. Then, with the help of her squires Gilbert Bolden III and Preston Chamblee, she removed her carapace. Now in a simple beige dress, she danced an anxious solo. Though the music was legato, Phelan executed fast jumps and turns. She mimicked the angular motifs of her progeny, who jutted their elbows and knees like bent wings. Pires’s commitment to avian themes was thorough; they were prominent in the title, the choreography, the styling, and even the score, by Jocelyn Morlock, which included the composition, “Oiseaux bleus et sauvages.” (The music was conducted by Andrew Hilary Grams, with beautiful performances by cello soloists Stephen Perkyns and guest artist Coleman Itzkoff.)

Phelan’s aides joined her for an adagio pas de trois in which she pulled away from them like a ship figurehead. The stage filled with the entire cast, who were now all sporting extra plumes, and Phelan walked through them again as they moved slowly around her. When the curtain began to fall again, she ran to it, without her armor this time, and propped it up while staring down the audience until the theater went black.

Topically, this piece was radical. I am floored that maternal anxiety is the subject of a ballet on the NYCB stage. What a long way the company has come since the Balanchine and Peter Martins eras, when ballerina parenthood was discouraged (the men have always been allowed to procreate—as it doesn’t take them offstage or alter their physiques). In a relatively short amount of time, the company has gone from one or two very senior ballerinas getting away with having a kid to a veritable baby boom throughout the ranks (meaning a few dancers per position). Phelan herself has an 8-month old.

Pires’s work also demonstrated a welcome evolution in the ballet mother archetype. The handful of mom roles in the rep are prop-like, as in the ruffed and bustled queens of “Swan Lake” and “Sleeping Beauty.” Often royals, they have symbolic authority but no depth. (Pires nodded to this trend at first, with the empty dress and one-note signage.) The “Nutcracker’s” two mothers, Mother Ginger and Frau Stahlbaum, are also big-skirted drill sergeants—one cartoonish and one kindly. Though Stahlbaum does get that lovely midnight display of maternal tenderness (I’ve heard that she was originally stiffer, until Heather Watts convinced Balanchine to literally let her hair down).

Are there other mothers? Not many. The mothers in Jerome Robbins’s “Les Noces” sob as they orchestrate their children’s arranged marriage. There’s aloof, lustful Lady Capulet. Oh yes, and the Queen in Jerome Robbins’s “The Cage,” who instructs her daughters in sex and cannibalism. Pires’s closest analog would be another worried bird mom: the Cuckoo in Christopher Wheeldon’s “Carnival of the Animals,” waiting up all night for her missing chick. Pires’s Mother hinted at all this baggage before adding yet more complex maternal woes: stress, loneliness, vulnerability, ferocity.