אורח חיים שט״זOrach Chayim 316

Se’if 1א׳

הַצָּד צִפּוֹר דְּרוֹר לְמִגְדָּל שֶׁהוּא נִצּוֹד בּוֹ, וּשְׁאָר צִפֳּרִים, וּצְבִי, לְבַיִת אוֹ לְבִיבָר שֶׁהֵם נִצּוֹדִים בּוֹ, חַיָּב; וְאִם אֵינוֹ נִצּוֹד בּוֹ, פָּטוּר אֲבָל אָסוּר.

1. When Trapping an Animal Is Forbidden on Shabbos and When It Is Permitted, 12 Seifim: 1. A person who traps a sparrow in a cabinet into which it flew, and other birds, and a deer in a house or a roofed coop and they are trapped in there, is liable. If it is not trapped in there, one is exempt, although it is forbidden.

Se’if 2ב׳

צָד צְבִי יָשֵׁן אוֹ סוּמָא, חַיָּב; חִגֵּר אוֹ חוֹלֶה אוֹ זָקֵן, פָּטוּר. הַגָּה: הַמְשַׁסֶּה כֶּלֶב אַחַר חַיָּה בְּשַׁבָּת, הָוֵי צֵידָה (כ"ב); וְיֵשׁ אוֹמְרִים דְּאַף בְּחֹל אָסוּר לָצוּד בִּכְלָבִים, מִשּׁוּם מוֹשַׁב לֵצִים (תְּהִלִּים א, א) (אוֹר זָרוּעַ גמ' ע"א דַף י"ח).

2. One who traps a deer that is sleeping or blind is liable. If it is lame, sick or old one is exempt. RAMA: A person who sends out a dog to hunt a game animal on Shabbat - this is considered trapping Kol Bo). There are those who say that even during the week it is forbidden to do this with a dog for this is conduct befitting “a company of scoffers.” [Note: See Tehillim 1:1. As that verse indicates, this is considered as undesirable conduct. Torah Law strongly frowns upon, and according to some views, actually prohibits, hunting for the sake of sport.]

Se’if 3ג׳

כָּל שֶׁבְּמִינוֹ נִצּוֹד, חַיָּב עָלָיו; אֵין בְּמִינוֹ נִצּוֹד, פָּטוּר אֲבָל אָסוּר. הִלְכָּךְ, זְבוּבִים אַף עַל פִּי שֶׁאֵין בְּמִינָן נִצּוֹד, אָסוּר לְצוּדָן. הַגָּה: וְלָכֵן יֵשׁ לִזָּהֵר שֶׁלֹּא לִסְגֹּר תֵּבָה קְטַנָּה, אוֹ לִסְתֹּם כֵּלִים שֶׁזְּבוּבִים בּוֹ בְּשַׁבָּת, דְּהָוֵי פָּסִיק רֵישֵׁיהּ שֶׁיִּצּוֹדוּ שָׁם (בה"ת וּמָרְדְּכַי סוֹף פֶּרֶק כִּירָה וְאָגוּר). וְיֵשׁ מְקִלִּין בְּמָקוֹם שֶׁאִם יִפְתַּח הַכְּלִי לִטְּלָם מִשָּׁם, יִבְרְחוּ (טוּר).

3. One is liable for trapping a species that is usually hunted, and it is Rabbinically forbidden to trap species that are not usually hunted. Therefore it is forbidden to trap flies even though they are a species that are not hunted. RAMA: Accordingly one must be careful not to shut a small box or close a Keili with flies inside on Shabbos, because it is a Pesik Reisha that they will be trapped within [Ba'al HaTerumah; Mordechai]. [Note: a pesik reisha (Lit. cutting off the head) is an action that ordinarily would be permitted but which will definitely cause as an unintended side effect an action that would be forbidden]. There are those who are lenient in circumstances where upon opening the Keili to grab them they would escape. [Tur]