Ivy seems to prefer some trees more than other. It loves Doug Firs and Big Leaf Maple. It climbs Western Red Cedar as only a last resort. We have found definite growing edges in Forest Park. These seem to be related to contour lines.
Berries are toxic to most native song birds.
Our suspicions need to be further verified. We hear that is yellow-jackets. We need both literature and internet searches. We need additional and expanded compilations of available information. We need to produce an extensive Ivy FAQS with supportable answers.