Are plastic particles reduced in size in seabirds' stomachs?

Many studies have quantified plastic loads in seabirds' stomachs but provide imprecise estimates of retention time. Quantifying retention time is fundamental for assessing biological impact and for the use of plastic as bioindicators of plastic pollution. Presumably, plastic is retained in the grinding section of the stomach (gizzard or ventriculus) until ground small enough and particles then pass into intestines and are defecated.