"Bird dropping" publications are minor translations,* very short, undeveloped papers in out-of-the-way journals or conference proceedings, encyclopedia articles, interviews, or any other kind of publication that is not a well-developed article that you would be proud of. The problem is that a list of many such publications on a c.v. makes the c.v. look padded, especially in the absence of more substantive work. Imagine the effect on a reader of a c.v. that look like a list of 14 publications, but on closer examination yields only two pieces of any real substance.
Another mistake people make at early stages of their career is to list all their publications under a single category.
I've ended up with more items like this on my c.v. than I would have liked, but I also have a long list of refereed articles and book chapters on my c.v. before the category of "other publications" even comes up. Some of my minor publications are important to me, like a few things publisehd in Insula and Revista de Libros in Spain. I've also done many book reviews, before cutting back a few years ago. None of them is impressive per se, but they add up to something by sheer bulk.
*Obviously a translated book will be more impressive than a translation of an interview with Carlos Fuentes published in your Graduate School student journal.