For now Stilwell will only say that the fossils seem to resemble modern seabirds known as cormorants.
"They look very tall and slender," he said. "We have one little guy who was probably no more than 30 centimeters [12 inches] high."
But "we've got one that is over a meter [three feet] tall, and we've got other bones bigger even than that."
In fact, the excavation uncovered bones that are too large to belong to birds, including what could be the big toe from a two-legged carnivorous dinosaur known as a theropod.
(Related news: "Dino Fossils Found on Remote South Pacific Island" [April 3, 2006].)
Paleontologist Joan Wiffen, who was not involved in the new work, discovered the first evidence of terrestrial dinosaurs in New Zealand in the 1970s near Hawke's Bay on North Island.
Wiffen said that any information on New Zealand's Cretaceous birds would be new, because the fragility of bird bones means that they are very poorly represented in the fossil record.
"It's also great to have a second dinosaur site in New Zealand, so we can get a better understanding of what conditions were like," she said.
"At least half the dinosaurs had to be herbivores to keep the food chain going, so analysis of leaves and seeds and wood will help to tell us more about the environment at that time."
In particular, excavation leader Stilwell is hoping that the new fossils can provide more evidence for land bridges between the Chatham Islands and mainland New Zealand.
The rock layers containing the seabird fossils were probably once part of a shallow marine environment, he said.
But "the dinosaurs and birds needed land, so they were probably living and breeding and dying fairly close by," he said.
"Maybe at some point there were emergent islands there, but if we had really big dinosaurs there had to be sufficient land to keep these species going."
About 80 to 85 million years ago a densely forested land bridge is believed to have spanned the Chatham Islands and present-day Banks Peninsula on South Island.
"There probably also had to be a connection between [the Chathams and] somewhere like Hawke's Bay, because of the dinosaurs that were found there," Stilwell said.
"I'm hoping that if we find enough bones, that we can make that connection more concrete."
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