The Bird Catching Tree

​We're all entranced by the sights and smells of the flowering plants.  The Angiosperms or flowering plants have been attracting pollinating insects since the time of dinosaurs (The Cretaceous).  The showy flowers entice birds, bats, butterflies, bees, and moths with the promise of juicy nectar and nutritious pollen.  In return, the flowers only ask that their pollen be spread from flower to flower with the hope of fertilizing the next generation of seeds.

​​Should seeds develop from successful pollination, the plant's next task is the dispersal of its propagules.  In temperate zones Maple trees create "Helicopter Seeds" which spin wildly away from the parent tree riding the wind on their way to the forest floor.  Oak trees create acorns which are then carried all over the forest by hungry squirrels and birds.   In Palau, the primary mammalian disperser is the fruit bat, which can carry Pandanus & Breadfruit seeds to the most remote corners of the rock islands.  The colorful fruit dove is more than happy to get carry the delicious fig fruits high up into the canopy of a host tree.  The Mangrove & Littoral zone trees, shrubs, and vines use ocean currents to get their progeny from place to place.  The coconut is perhaps the most famous example of an ocean dispersed seed.

​The creativity of the plant world seemingly knows no boundaries.  The genus Pisonia is represented by two species of trees in Palau.  The coastal Pisonia grandis can grow to staggering heights on the beach fronts of Kayangel atoll, but is essentially stunted on the limestone islands.   It's forest dwelling cousin, Pisonia umbellifera, hides in the understory of the old growth forests, reaching heights of less than 25 feet.  Both species achieve pollination using a rather unpleasant aroma which attract flies as their primary pollinator.  But in terms of seed dispersal, the Pisonia genus takes a darker turn.

​The seed cluster of Pisonia exude a sticky resin which can act like a miniature LaBrea Tar Pits, trapping small insects and even reptiles.  But the goal of Pisonia is the hunt for big game:  Birds are their primary target.  Innocently alighting on a branch, the bird's feathers get caught on the seeds forcing the victim to flee in panic.  More often than not, the sticky glue of the seeds adheres to the bird, until the feather is lost.... thus successfully dispersing the seeds.

​On occasion however, the bird is unable to free itself from the clusters of seeds.  As the bird struggles for freedom, it only becomes more deeply ensnared by the sticky glue.  Ultimately the bird becomes exhausted and perishes on the forest floor, providing not only the desired dispersal, but the bonus of fertilizer for the germinating seeds.  

On May 16, 2019 a group of visiting students and professors from Redlands University were able to witness this drama unfold on the island of Ulong.  While hiking into the forest to inspect an ancient village site, the students watched a young Collared Kingfisher hop through the forest in obvious distress.  The team of students gently captured the struggling bird by wrapping it up in t-shirt.  Upon closer inspection, it was obvious that the Kingfisher had become ensnared in a cluster of seeds from the bird catching tree.  With great affection, the students removed the seeds using coconut oil.  The beautiful blue Kingfisher eventually regained its composure and flew back into the forest accompanied by cheers and applause from the students.

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​The Palauan name for Pisonia umbellifera is "Uudeuidarbekai" which translates into "the sticky glue of the megapode."  The Megapodes are a chicken like bird which feed on insects and fruit in the forest understory.  They frequently step on the fallen seeds of Pisonia during their forest walks and bounce around wildly trying to free their oversized feet.

By: Ron Leidich